It would be unlikely to be a 5 am start - more likely a staggerred start from about 8am onwards, maybe with afternoon options as well. That was what was offered for 2009. The organizers seem ahead of the game this time, and have already taken measures to relieve some of the bunch points for sleeps. Last time the weather (so bad at one point that at Eskadalemuir on the return riders were strongly advised not to leave, for their own safety) and the timing (outbound and return riders meeting) meant that some of the northern controls were overwhelmed. 2013 will involve a loop in Scotland rather than an 'out-and-back'. The amount of sleep you get and your ability to meet timings for hotel bookings obviously depends on your speed.
Last time my sleep stop times were something like 12:30am-5 (Thorne), 12-5 (Eskdalemuir), 23:00-4:30 (Alston) and 21:30-5:00 (at my Mum's between Thorne and Lincoln) - though not all that time was sleep. I'm not fast enough to have the confidence of hotel booking beyond the first night, and even then wouldn't bother. I don't seem to have a problem sleeping on a floor after 300km+ of cycling. Earplugs and eyemask help, though.