So individuall, impossible to answer.
A lotta women are hot in their 30s, some are still hot in their 40s, few are hot in their 50s, 60s is getting tough....
Funny thing is, when I was younger I was lusting for Milfs big time, but now that I'm older (26; I'm looking very young tough 21-22) I start lusting for teh teenage pussy more and more again and go out picking up 16-17 yr olds at the weekend. No clue why that is.