At the beginning of The Muppet Movie, Bernie the Agent convinces Kermit to try out show business by suggesting that Kermit "could make millions of people happy." In general, it's common for people to do nice things for others, such as giving gifts or telling jokes, with the motivation of making others happy. But do such things actually make people happier in the long run?
The idea of the hedonic treadmill is well known, and I'm not an expert on the science of it. Here I'll just discuss how my own subjective experience agrees with a "hedonic treadmill"-type view. This page should be considered a random blog post for which I haven't done any scholarship.
In a YouTube comment I can't now find, someone said that he limits his consumption of ASMR videos because the effect diminishes over time if he does it too much. 
Of course, similar trends are true for tasty food, sexual pleasure, and just about any other source of enjoyment. It's possible that this is just sensory-specific satiety, and that new sources of stimulation could provide new bursts of pleasure. However, based on my own experience, I think there's also a general trend that if you experience a lot of pleasure now, you'll experience less pleasure some time later to make up for it, perhaps with some exceptions. For example, if you have an awesome weekend partying, then you may feel less pleasure from working at your job during the subsequent week than if you have a more sedate weekend.
The situation feels sort of like having a finite "pleasure budget" that you can spend on different activities. The more intense the pleasure is, the more "pleasure points" you spend at once. And as with passing the "Go" square in Monopoly, your pleasure budget gradually replenishes itself over time. If you've used up all your pleasure points and feel temporarily anhedonic, then you have to wait a while for your "pleasure bank account" to fill back up.
The tendency for pleasure now to reduce pleasure later is sometimes mentioned in contexts like drugs and pornography where people love to moralize. However, I suspect that the trend is true for basically everything, including the pleasure that your grandma feels when receiving a nice card from you. It would be surprising if this weren't the case, since I don't think the brain distinguishes between "wholesome" and "unwholesome" pleasures when performing hedonic adaptation. (I put "wholesome" in scare quotes to indicate that I'm not a fan of moralizing regarding pleasures, other than to warn people that, e.g., some hard drugs can actually mess up your life.)
Because of my subjective experience of a roughly fixed pleasure budget, I'm skeptical that many things people do to make themselves or others happier actually increase total, long-run happiness in their lives. Likewise, this view suggests that a certain amount of asceticism isn't necessarily depriving oneself of pleasure after all, although for ascetics, pleasure is probably doled out mostly in small doses rather than in big bacchanalian bursts. (By "asceticism" here I mean only forgoing certain pleasures, not, e.g., wearing a cilice.)
If you find that you're not motivated to do something "boring", like working on your taxes, one strategy can be to spend a few minutes doing a physical task like house chores with no music, no podcasts, and no other forms of stimulation. This can help to "reset" your brain's expectations about receiving constant squirts of pleasure, which adds points back into your pleasure bank account. Then, when you do work on your taxes, the stimulation they provide will be somewhat interesting relative to the absence of stimulation you had previously.
Apparently some "NoFap" proponents report that something similar happens when giving up masturbation:
[Those who do NoFap are] able to experience pleasure in the small things much easier. Just making eye contact with a girl, it's so pleasurable. Just talking with a girl is so pleasurable. Just hearing a bird chirp is so pleasurable. Just hanging out with your bros, hanging out with whoever, is so much more pleasurable because you're not used to that totally out-of-this-world pleasure hit that you get from whacking off.
Personally, I'm not much of an ascetic mainly because it's difficult and annoying to avoid temptations. If you're craving a pleasure you can't have, it's hard to get useful work done. Thus, I see the main value of pleasurable activities as being their craving-elimination function rather than the pleasure they provide, because, as mentioned, I'm skeptical that pleasurable activities generally do increase total pleasure over time, at least within typical, healthy human minds. (This skepticism is based mainly on my own personal experience, and I'm not making any strong claims about this viewpoint actually being correct.)
This view can be spun into a "glass is half full" message: if you feel disappointed because you didn't get something that you thought would make you happy, then you can feel less bad about the situation, because not being made happy now means you're saving up pleasure points for later!
I'm less certain how well the "fixed pleasure budget" idea extends to people and animals who aren't already near the top of Maslow's hierarchy of needs. It seems pretty clear that depression and certain other mental illnesses reduce an individual's long-run happiness levels, and I don't think people feel unusually high amounts of pleasure once they recover from depression. Plausibly deficits in sleep, nutrition, and other fundamentals would also limit the size and refill rate of one's pleasure bank account.
It also seems doubtful, based on my own experience, that feelings of suffering lead to later increases in pleasure, other than very mild relief that the pain has stopped. In other words, pleasure budgets seem to cap the total amount of pleasure it's possible to experience, but it's not the case that everything that reduces welfare is compensated by an increase in later pleasure. Perhaps suffering doesn't increase your pleasure bank account, and maybe the only thing that increases your pleasure bank account is the passage of time? In other words, life grants you a fixed "pleasure allowance" per day that you can spend and/or add to your savings. According to this terribly oversimplified picture, the net hedonistic welfare of a person's life would be
(pleasure allowance per day) * (lifespan) - (whatever suffering was experienced during life).
Situations like depression may turn off the pleasure allowance for some period of time.
There's an interesting further question of whether pain works in a similar way as pleasure. Do we experience a given amount of pain (a "pain debt") that can either be paid off now or in the future? In many cases, there's some extent to which experiencing pain in the short run can inure one to pain later. For example, I think my experience with esophagitis at age 15 made me more resistant to more minor forms of pain for a few months or years thereafter. One might say that I had already "paid my dues". Ralph Nader suggests regarding campus political correctness: "what you do is turn people into skins that are blistered by moonbeams. Young men now are far too sensitive because they’ve never been in a draft. They’ve never had a sergeant say, 'Hit the ground and do 50 push-ups and I don’t care if there’s mud there.'" If this idea is valid, it presumably doesn't apply to situations like depression, and in many cases, early suffering actually increases later suffering by causing long-term trauma or other problems.
To the extent it's true that pain now can reduce pain later, what does this imply about altruistic efforts to reduce suffering? For one thing, this idea doesn't affect the value of reducing suffering at the end of life, such as by making animal slaughter less agonizing or allowing physician-assisted suicide, because end-of-life suffering won't offset any later suffering. Insofar as depression and certain other mental illnesses aren't subject to the "law of conservation of pain", alleviating them seems important. In addition, preventing organisms from coming into existence is still as effective as ever at preventing suffering. On the other hand, a hedonic-treadmill viewpoint makes efforts to, e.g., improve the comfort of people's lives look less promising than one might have naively thought.
It's plausible that "pain now means less pain later" substitution isn't 1 for 1. For example, maybe 10 units of pain now only prevent 5 units of pain later. In this case, reducing even mundane pains would still be somewhat valuable, though maybe only half as much as we thought.
And of course, these considerations only apply to minds that show hedonic adaptation. Depending on how useful hedonic adaptation is, artificial worker machines of the future may or may not have analogues of it.
Finally, I should add that when I talked about "amounts of pleasure" in this piece, I had in mind the kinds of rough magnitudes that one would assign if trying to describe intensities of experiences. I don't intend to suggest that pleasure is precisely or objectively quantifiable, nor that the moral value of an experience should be the same as its number of roughly estimated "pleasure points". For example, one might hold that a single instance of falling in love is more morally valuable than any number of pleasure points spent on muzak and potatoes. Or, closer to my own view, one might believe that a single instance of unbearable torture in which the victim would give up anything to make the pain stop is more morally serious than the moral value of spending any number of pleasure points.