Thank you, I really appreciate the response! The model makes complete sense now that I have this context, especially thinking of it like the pledge drive model. That was kind of an "aha!" moment as well as an "I feel like a jerk now" one :P

In fact, a very generous user bought me two months of paid time, and when that expires I will definitely go in for a yearly subscription. This site is wonderful, and you guys are wonderful for all the thought and hard work you put into it.