Great marital lovemaking is, . . . well, . . . great. There's really nothing like it. So how much pleasure should we be trying to attain in the act?
I think the answer is simple, but not that helpful: we should aim at "enough."
"Enough" means that there is a natural physical goal in the act (as well as other goals). That goal is 1) climax (for both partners), and 2) more generally, “delight.” So we should aim to engage in an act that is, among other things, pleasurable and physically and psychologically fulfilling. If we achieve that, we've achieved the ordinary physical dimension of the act.
Implicit in this "enough" is: don't worry about how much, at least if you have enough. The problem is that, if you focus on having "more" or "an awful lot" of physical pleasure, you face three problems:
1) it may establish desires that are unachievable, and so create expectations or hopes that will be frustrated, even from a purely physical perspective. Focusing on maximizing the pleasure is likely to lead to some great physical sex sometimes, but it will just as surely lead to a good deal of really disappointing physical sex.
2) The focus on the "more" you want (that you don't have now) may lead you to fail to appreciate what you do have. It is so easy for human beings to take what they have for granted and focus on what they don't have. For example, a husband may be disappointed that his wife is not as intent on having sex frequently as he is, or that she is not as adventurous as he would like her to be, not as interested in variety. But that same wife may be so focused on her love for her husband that she gets caught up into the act very powerfully and finds it very satisfying -- and that is one of the most satisfying pleasures of sex for a man. And she may do this even though her husband is also disappointing to her -- e.g., the quality of his "foretalk" may leave a lot to be desired.
3) it's hard to prevent a dominating desire for “more” physical pleasure from displacing more important parts of the act -- the emotional, intellectual, and spiritual unity, not just the physical. Most importantly, focusing too intently on maximizing the physical will make the sex not only less spiritual, but less human too.
Now, if you or your wife are just plain bored during marital lovemaking, you should do something about it! And especially if your wife is regularly failing to achieve ordinary physical fulfillment in the act – the explosion of pleasure and delight that is orgasm – you definitely ought to do something about it. (And it's usually not that hard to do that.) But if you are both finding sex enjoyable, pleasurable and finally satisfying, then the best thing to do is not to worry overly about the physical side of it.