I started less than a month ago in an MMA program and my instructor is letting me test for my first belt (yellow) on May 6th. I do have a little previous martial arts experience, but not for 18 years!!! I probably hit harder than many of the other white belts and have pretty good technique, but I can think of at least one other that is probably better than myself.
I would just express this concern when shopping for a school. There is absolutely no reason (unless you totally suck) why a person shouldn't be able to test for at least one belt in a year. If you feel you're reasonably skilled and your instructor holds you back that much, then you're monthly income to him and not a student he's serious about imparting his knowledge on. If someone is milking you...walk! Also ask about school infiliations and stuff. For example, I am studying under a black belt from Dan Inosanto and, hopefully, I'll have an orange belt by the end of the year and, when I move in November, find a school that will respect my rank and allow me to continue progressing.