Well, it'd be nice if you backed that "After 30 you are dead to your genes" with something more scientific. Because it does not make sense, really. Menopause is still some 20 years away, and even then there's evolutionary advantage of living, to provide to your offsprings and offsprings of your offsprings (hence why women live longer than men, even after menopause), see [1]. If anything, you're very much alive to your genes at your thirties, only that genes require you to focus not as much on you finding a mate. By this age, your genes assume, you have found a mate and probably have procreated at least once. So the focus shifts to providing for your progenies, and social aspects, such as "friends" ("potential ways to get laid" for your genes), naturally, wane. So you're right about that part, that it's probably evolutionary predisposition to make friends at younger age to find a mate; having said that, I have reasonable suspicion, though, that your statement "After 30 you are dead to your genes" is grossly incorrect, though.
[1] https://en.wikipedia.org/wiki/Grandmother_hypothesis