I deleted the comment I posted because someone laugh reacted it, and I don't want that reaction to stay on my comment, it's honestly rude and annoying when people do this without responding..
I was mentioning that I consider someone a regular client if he books me once at least once month over a period of at least 4-6 months.

But that's not always the case. I have clients I've seen a less often but for over a year. I have one client that I've seen since the very beginning, I appreciate him a lot and he books me for short periods of time, sometimes we go a month or two without seeing each other, but we always end up reconnecting.
To me there's a difference between a regular and a repeat client, some clients will see you a few times over a few months and move on to another SP or something else, which is also fine. I also have clients I've seen a few times over the course of 1 to 3 years, when they're in town. Maybe they would be regulars if they lived here. I always appreciate seeing them.