According to my anally retentive punting record spreadsheet (I'm not the only one, am I...?):
My most visited regular is 33 times over the last 5 years. Although we have our familiar routines, I can honestly say I'm not bored of her. That said, I don't see her more than monthly, really, which helps. And even with the familiarity there are frequent twists on what we get up to which avoid boredom. While she still continues making me come like a train, I'll carry on going back.
Number 2 is 17 times, over a similar period.
Number 3 is 15 times in the last 3 years.
I have to say, I've become a creature of comfort in more recent years, keeping with old familiars, where I know I'm going to get a good service. Too many one-offs have sold me down the swanny. Just a shame about the other faves who've retired. There are another 4-5 who, between them and the current ones, would be all I wanted if they were still working.