No problems with my DK ring here either, and my ring has lots of pave. I've worn it daily (including often sleeping in it, which I know isn't the best for the prongs) for a year and a half. I expect that eventually I'll have to get one replaced, it's just the nature of pave, but I think it's significant that every single one of my friends who have pave rings from big box retailers have had to have at least one stone replaced and I haven't yet.
The turn around time is just part of the custom process. Think a week or so to get CADs done, tweaked, and approved, then the ring has to be cast, then all those tiny little pave stones set and the ring polished. I think David keeps a pretty full schedule, so your ring might have to wait a little bit behind others in the queue, which might be part of the reason for the wait.
Good luck with the whole process! Let us know how it goes