I used to be over 6 inches and very thick for my length. Around 50, I started not getting as hard but never really noticed a decrease in length until well into my 60's and at 76 now, I am 5 inches at my best. My girlfriend 75 is quite tight but with a cock ring I can still penetrate her when we want. Viagra does very little for me at all but a week ago, without a cock ring and only my balls bound with one to hold them down for her to play with I had a very serviceable erection. maybe the Ghee I have been eating is finally doing what it is supposed to. I get a testosterone booster shot once a month but doc says it wont make a dick hard but raise my sex drive. I don't need it for that but rather to help maintain muscle mass. I can rarely cum anymore fucking her but she prefers oral sex
and I cum every time. Less than half as much cum as in my prime and it only runs out instead of shooting all over.
I have a foreskin fetish and an uncut buddy that I love to make his cock feel good various ways(no anal). He is about 60 now and his wife only puts out about 6 times a year. I get about the same penis performance when I am with him. He still gets a pretty good erection but not quite the performer it was when we met about 15 years ago having a 3-some with an earlier girlfriend. Not quite as long and he gets a slower erection.
I'd consider a penile implant with the kind they have now. It used to be if you got one it destroyed your ability for a natural erection ever again. Now they do it so you can have your cake and eat it too. No idea about the cost.