Hi woman of courage, of course asking a man that question could give you a good clue and of course if any man who wants to answer that it would also be helpful.
In clinical terms though it depends on the man and of course there are factors such as depression can cause a low sex drive or other problems that may be going on in his life. A man’s testosterone level do drop as he ages and yes this could also be a factor in low sex drive and not thinking about sex as often. When the testosterone decreases the man also becomes less aggressive. there are men however in their 80's that still have a sex drive and think about sex, so that is a tough question.
Hope that helped.