Hi nicholson,
I'm afraid this situation is becoming more and more common, with claimants waiting many months for decisions. Their is no official limit on how long ATOS and DWP can take with this process I'm afraid.
We do suggest that claimants make their MPs aware of this situation. Even if they can't/won't help (and some do), at least they should be aware of how the system really is (or isn't) working!
Contacting your MP