I'm 54 years old and I feel like I'm in my 20's, I want sex all the time, but the guy I've been with for 12 years doesn't really want it as much, maybe every 3 to 4 days I get lucky,
We are both the same age.
Does age have something to do with this?
When I was going through menopause I didn't want it, and he wanted it all the time,now that the doctor has put me on prempro I want it all the time. And he doesn't want it all the time like he use too. So what's up with this ?

In your 50's... I'd say its likely age related. However there are conditions that start to show themselves in that age range that can be contributing factors. I assume he gets regular physicals and has no medical issues.