I agree. A four month moratorium following a "Keep", or two months after a "no consensus" seems plenty to me. Maybe 6 and 3 respectively.
I don't think "no consensus" AFDs should delay anything, there should only be a delay if there is a positive decision to keep. I'd say 3 months is probably enough - a lot can change in 3 months.
If someone isn't happy with the result of a recent AFD, we should have a process by which it can be reopened (ie. not a new AFD, but continuing the old one, on the same page, previous comments still count). Someone would propose reopening the AFD and would have to give a reason explaining what has changed (reasons to delete/keep should be ignored at this stage). If people agree that something significant has changed (that could be some real world change in the subject making it more notable, for example, or it could just be a change in community consensus demonstrated by a similar AFD resulting in an opposite decision) then they vote to reopen. If the is a consensus to reopen, then the AFD carries on from where it left off, just like when an AFD is relisted at the moment.
It should be made clear that this is a different process to DRV - DRV is for when you disagree with the determination of consensus, reopening is for when you think consensus has changed.
The key thing with this proposal is that the comments made the first time still count after it is reopened (anyone who commented the first time round should be notified in case they want to change their vote), which should stop the "deletion by attrition" problem.