Hi Jen- I'm recently banded- 1/26/12, and it's the best thing I've ever done! The time frame can be anything from insurance requirements (I had to do a 6 month diet with my PCP) to health issues- any number of things. I was motivated, did what they told me to do as far as the appointments, the labs and tests (I just had the labs- cholesterol, vit D, etc and a chest x-ray and ekg- super easy), and the pre-op diet- and that will vary depending on your dr.
Good luck- and remember, it's a process, you still have a lot of work to do to make good food choices and exercise- it's not a magic bullet, but an extremely helpful and useful tool.