Compare this to martial arts, where instructors can say "In three months, you'll know some basic kicks and punches and will get this shiny yellow belt. In six months you'll be able to break wooden boards and will get this lovely green belt."
As someone who tends to start studying a few days before big examinations, my reward function definitely doesn't operate on a scale of even one uncountable eon, let alone three of them. Maybe it can wait the few months it takes to get a different color belt, but no more. When I get bored of meditating, thinking "this may pay off in three uncountable eons, assuming very sketchy ancient texts were mysteriously correct about the fundamental nature of the universe" isn't a very strong motivator. But to whatever weak degree I am goal-directed, it's always been about understanding what the heck the mind is - and to think that there's this legendary-monk-approved and scientifically-kinda-verified way of doing that (and simultaneously gaining a magical power) which I'm avoiding just because I don't have the willpower is pretty galling.
And I feel silly talking about it, because the party line has always been that if you're looking for rewards from meditation, You're Doing It Wrong. Desire is the root of all suffering, right action must be detached from lust for result, and one gains absolutely nothing from Supreme Enlightenment which is why it is called Supreme Enlightenment. Certainly it's official doctrine that the more you try to get something from meditation, the less you'll end up getting; there's even a suggested form of meditation in which you sit quietly, notice whenever you're trying to meditate (in the sense of "actively pursue some state") and make yourself stop.
You could not design a better way to frustrate human reinforcement learning. Which could mean that's exactly what it is - a technique to rewire the reward system. And that's all nice and well, but it's why I've never been able to seriously pursue meditation for more than a few months at a time.
It's also why I've had much better luck with lucid dreaming. As a very Western skill (some Buddhists did invent it way back, but most of the lucid dreaming literature around was developed by Westerners independently of the older traditions), the "avoid craving for reward" attitude has been replaced by your standard Protestant work ethic. Books even make promises like "If you work at this hard enough, you'll see results in a couple of months", and those promises have proven mostly true. And some of the skills involved - attentiveness and concentration - are a lot like the skills involved in meditation and I'm hoping they cross-fertilize.
And recently I have learned from muflax's blog about the jhanas, which seem to be that elusive meditative equivalent of a green belt - something difficult enough to work for, but easy enough to be accomplished in fewer than three uncountable eons. And apparently the state is pleasant enough to be instrinsically rewarding once you reach it. Sure, that teacher says "the likelihood of you experiencing a jhana is inversely proportional to the amount of desire that you have for it", but that seems like an acceptable level of perversity to put up with at this point.
One thing I've liked about that same cluster of Buddhist teachers are their works on how to avoid getting magic powers. I feel like any religion with explicit teachings on how to not have magic powers is a religion one can trust.