No desiderata, you are entirely correct about the putting it off makes you want it more. And makes you more likely to use them, because you've been picturing yourself using them for so long.
For me, I'm not setting weekly or pound markers. Nothing that regular. But I do have a "If I'm down a size or two before my vacation at the end of summer, I WILL buy a new swimsuit" goal. For me, taking the rewards as they seem right works best. When I can wear size 12 again, I'll buy new clothes. That kind of thing. I recently bought new running shoes because I picked up a new program, have been sticking with it, and so needed them. It was not because I met some arbitrary number. So I hope the rewards will keep you motivated, but for me, the regular ones don't work at all. I'm more motivated by the goal itself- to be happy and healthier. How does splurging on a haircut help that? (Noooo disrespect to those that need this motivation, mind you. Whatever works for you.)
If you really want to keep the rewards, I don't think they will motivate you much if you don't have a clear idea on what your working for. "Money" (that you barely spend as is) doesn't sound like a motivator in itself. "Money" is too vague, too easy to say, "So what...?" Think of what you want to do with the money (like my swimsuit) and it might motivate you more than just cash. If you can only think of things that you "might kinda sorta wanna" spend money on down the road, then maybe money isn't the right type of reward. What else might be a "treat" for yourself that you usually withold from?
That said, I agree with Shmead in that you do need to be looking at the long term, and the only way to achieve a healthy lifestyle for life is to pay good attention to the choices that go in to it. You need a plan of some sort. Think about it some more. You sound both young and smart. I'm sure you can achieve your goals.
Mini-Goal 1: 173 by 9/1/10 (Met!)
Goal: 125 by 9/1/11