LauraOh, your mom sounds great! Wish she were in my neighborhood. I'm about 10 years younger than your mother -- I could be her young stud! And what do you mean she doesn't want just a quickie? She wants a long-term relationship, or sex that lasts a long time?
Our comments illustrate the general problem many of us face. As we age, loss of libido (for whatever reasons) does not affect us all evenly. Yes, a lot of guys slow down, but not all. And a lot of women lose interest, but not all. The problem is that usually, the HD ones aren't married to each other! Nobody could know, when they get married at 25, if they'll have a high libido 40 years later! In fact, many will divorce long before 40 years because their libido levels grew apart.
I don't think you should have too much trouble finding someone in your age range who wants lots of intimacy and sex and can deliver it with no physical problems. I'm in my late 50's and I've yet to experience any significant change in my physical or mental sexuality. I realize I might not be the norm, based on all the Viagra commercials targeted for men in my age range. If anything, I could sometimes use a pill to cool off my arousal which might occur when I'm at work and just trying concentrate on my spreadsheet when an erotic thought pops into my head. Pretty much the same level of libido and response I had as a teenager. It's hell sometimes dealing with a high libido, but I'm not complaining.
So I'm here to tell you that there was at least one guy who was once 47, and who was good for another 10 years of sex every day, with intercourse lasting as long as you want. No Viagra needed, thank you. And I have to say with a laugh, I don't dare to try the stuff, not even once out of curiosity. I'm sure I'd be one of those guys who gets rushed to the hospital with a problem that's been going for more than 4 hours, and the nurses would all be having a chuckle at my expense.