From multiple times a week to once a week, bi weekly, once a month.
At this point I enjoy much longer dates so frequency is once or twice a month! Budget restraints when you are retired are a factor!
I don't think I will ever stop enjoying the company of a like minded vixen!

As I've turned the corner on 60, the desire is certainly there, but, I find that sleep and the effects of jet leg, are becoming more important factors.  I find myself deciding not to hobby because there's too much effort involved.  I do travel to Europe frequently, where, for the most part, any type of hobby activity is legally available almost 24/7.  "I'm too tired tonight; maybe tomorrow night..." is more & more becoming an option.  Because of my travel schedule, I have lost any sort of domestic track record here in the U.S..  Today's best practices (P411, etc) make a quality session much harder to arrange, if not impossible.  

I think the last time I was able to arrange a session was in Sept 2013 in Maui where I met up with a traveling lady.  I tried to find her to ask for a reference a few months back and found out that she's had legal and personal problems, is no longer providing, and is in jail.  Other ladies who rocked my world 10+ years ago have retired.

So, to answer the original question:  Over the last ten years, I have gone from one session per month to a mixture of 5-6 times per year in Europe + the rare session here in the U.S.

I try for once a week and sometimes twice a week if I have about 3 days in between. That of course doesn't include a couple of duos with 2 sweeties. Hey,You ask how many times do I SEE a provider. Counting OffTC I see them much more than twice a week.