I decide my discounts on a client by client basis. If a guy is easy to please in a private his tk/min cost will be a bit lower than a guy that comes in, nitpicks everything before he can even get to know you, makes crummy demands and then tries to get you to do a laundry list of crap that's in your bio that YOU DON'T DO!
What I'm trying to say is: become a frequent flyer. We know, we remember, and we'll reciprocate our thanks as we can.