Why players get out of the game
It's not the post's title, but it is a title.
I don't think there's a definitive length of time an individual guy "should" be a player. That length will vary by guy. Male peak sexual market value (SMV) also tends to peak much later than female SMV. A forty-year-old woman is on the verge of infertility while a forty-year-old man remains potent and in some ways likely more desirable than he was at 28. Given enough time, however, everyone's SMV declines to zero. Mortality's reminders probably drive more men off the game than anything else. Look at most guys age 50+... their families and especially children seem to provide much more meaning and significance than banging the latest hottie. That doesn't mean a guy should turn 40 and quit. But it is worth looking at people throughout the age spectrum and contemplating what will matter at age 50 or 60.
For most 20-year-old guys, everything above is immaterial: "Who at 20 would understand the world through the same lens as a 40 year old man just because they share a common pastime?" When I was 20 I thought knocking off skirt would be the be-all, end-all for my entire life. Now I am not so sure, and I have a "rambling" category on this blog describing those feelings.
It's also possible to try co-parenting or similar arrangements, giving space for a family and for skirt-chasing. I don't personally know any guys who have consciously done this effectively, but many divorced guys end up co-parenting by default.
If a guy eventually does want a longer-term relationship, the older he is, the older the chick has to be. Very few people are going to be in sustainable relationships with someone 15 or 20 years their junior. It's not impossible, it's just very unlikely.
Read the comments thread as well. Nash appears, which means epic and interesting comments. The comments on this one are as useful as the post.