Again, speaking only for myself, I think the age of the woman makes more difference than the age of the man.
Older women are much less likely to feel threatened by that sort of attention, and much less conflicted about their own attractiveness.
I’m probably going to catch all sorts of shit for this, but frankly, the thing with very young women is that their natural instinct to present themselves as desirable is at war with all the “evil, objectifying, male gaze” crap that their Wymyns Studies class has filled their heads with*, not to mention all the “stranger danger” and “boys only want one thing” crap they’ve all-too-often heard all their lives. Older women who’ve done their own lusting and objectifying have reconciled this in their minds. We understand that there really is a difference between “objectifying” and “dehumanizing”.
Also, in purely practical terms, the world is a much bigger and scarier place when you’re twenty than when you’re forty. A twenty year old can have very good reason to feel threatened by a forty year old, because there is a palpable imbalance of power and experience there. A twenty year old is still figuring out how she feels about herself, and other people still have input. At forty, I’ll take my "hey beautiful!"s from anyone between the ages of 18 and death and smile about it. It’s a fleeting comment, not a measure of my personal worth, nothing I have to try to integrate into my opinion of myself.
*Disclaimer - I am a steadfast feminist, but I object to the villification of men, and I’ve heard way too much of it from that sort of venue.