You are not old until you are twenty.
40 I think.
At 30-31, you are most physically attractive (research shows) unless you've massacred yourself exaggerating on life's problems. Possibly financially secure too, and most probably, have a family.
At 40-50, menopause. After that, if you have a good life partner, you and him/ her start growing younger again to discover whatever you missed of life because of the pressures of academia, career and child nurturing. If you have a bad partner, you sink into depression and eventually drown in it. So choose your partners well people.
As for me, I hate it when I am the only one here.
