There isn't a time limit, but....if you don't finish in a year, I think you need "new requirements" as they change periodically.
I would LOVE LOVE LOVE to do this!!!!!
See...also, I don't think that you really NEED a certain level of experience....you send your swatches/samples in, and if they meet the qualifications, then you pass that level, if not, they send back your swatches, tell you what needs to be fixed, and then you get to try again....and in my case...try and try and try. It is a constructive critisim kind of thing I gather???