90 year old guys who still are "interested' are looking at what all men are looking at - hot 19 year olds....

http://www.youbeauty.com/love/study-reveals-the-age-men-find-women-most-attractive-and-its-seriously-disturbing/

And at a more realistic level, guys I know of in their 70's who are out there dating, or working on wife 2, 3 or 4 - are with women in their 40's...