It's sad but the longer you're together... the more scarce. That is apparently the way it usually is. We've been together for almost 12 years now. Life gets in the way. Bummer.
It's different for everyone, of course, though that is the trend, and I've been there, for sure. My wife and I will both be 49 this year, approaching our 26th anniversary plus 4 years before that (college sweethearts), and we are having a bit of a sexual renaissance right now. She's in the early stages of menopause (perimenopause) and for the first time in all our time together, I can barely keep up! We're definitely having more sex now than we were 10 years ago, when our 3 kids were between the ages of 2-10, despite the fact I am in far worse shape/health than I was then.
I'm 60 years old and have been together with wife for 25 years. About 4 years ago she downloaded an app to keep track of our encounters. Turns out we do it on average of 3.5 times a week, so pretty much every other day. It's not always PIV but we both get off in most sessions. It's getting a little more difficult as I get older but so far (knock wood) no need for ED meds although I do juice with testosterone but that's more for exercise purposes.