The only problem I have with regulars is if they turn obsessive... I had what I called a "Pretty Woman" client last year, nightmare! He started off as very nice, but then wanted to see me regularly for dates, er, no. They are not dates, it's a booking. Anyway, he turned really obsessive so I cut him off and told the agency I was working for then that I didn't want to see him again.
I had a few regulars, and they were no problem at all. One of them who used to pick me all the time then moved on to one of the other girls. I spoke to her when she was going in to use the flat once, and I was coming out of it. She told me about my regular and how he grew to obsess over her, wanted to marry her etc. I felt really sorry for her
In essence, I think as long as they are not developing a heavy attachment to you, you should be fine. As Jan said, sounds like he likes you, but don't let it get to the stage like it did with me where he starts an unhealthy attachment!