I think it varies a lot. Right now he's pretty busy. I can tell because it's hard to schedule session outside our usual times.

He used to number his invoices. Then it was really easy to tell. But he lost track of that somewhere along the way.

I like it when he's busy, because then I feel secure that his private practice is doing well and he won't feel the need to think about outside work. But I don't like it when he's too busy to squeeze me in.

I know he has other clients. But I also know I'm his longest term client, and that I have a special place for that reason. So I feel secure enough to just feel grateful to the others for keeping him in business.