I think it really depends on the AMP. Every place is different. One mamasan told me the busiest days are when popular girls are working. Another said Saturdays were slow because nearby offices were closed. Others say that typically the place is empty and then suddenly five guys walk in. It's just the way it goes. I tend to walk in when the mood hits rather than make an appointment, but sometimes they are too busy for me.
I would guess that summers are slower as more people are away and it's too nice to be in a dark massage parlour. But then again, these places can be cold in the winter. I would also guess that lunchtimes can be busier as guys look for a quickie, as well as the after work crowd in the afternoons. I like to visit in the early morning when they open, but often there are only one or two working and they can be busy.
In other words, I have no idea.
There are a few places that don't advertise on LL, so they mostly deal with regulars and are maybe under the radar a bit. I live downtown and go to Roxanne's. They don't advertise but sometimes they are really busy. Still, I rarely see another guy there.