The implication of what you write automatically equates a quiet CVR with falling asleep.
CVRs in cruise often have long periods of silence.
Sure. But hopefully not in a scenario where the weather ahead was of some concern and other aircraft around were deciding to divert.
I believe the best explanation is one that incorporates all of the following:
1. Some inconsistencies in radio communications leading up to the crash, and no aircraft heard anything from AF447.
2. Apparent decision not to divert around weather (everyone else that night decided to divert)
3. Captain apparently not up front. Question for the pilots here. Would recognition of worse than normal weather ahead and the requirement to make an active decision about this (ie to either initiate a significant diversion or not to divert) generally warrant a call to the Captain if he was taking his rest break?
4. Subsequent sudden and catastrophic loss of control - for a number of possible reasons. But it was sudden and catastrophic. No radio calls. No signs of preparation for an emergency. CC not in their seats.the bridge
Much of the discussion on this thread starts at number 4. There are very likely to have been significant factors already in play well before 4.