I believe this is related to http://www.havenandhearth.com/forum/viewtopic.php?f=4&t=2305 and is also causing a lot of the raeg about recovering from travel too slowly.
After a long time (possibly the critter despawn timer?) of being logged out with one character, I log on with another, and go to the bed he logged out in. There is no sleeping hearthling in that bed. When I try to log on again as that hearthling "where you last logged off" I cannot do so.
I believe the sleeping hearthlings are being de-spawned, and therefore
a) Don't gain benefits of bed once they're despawned
b) Cannot log in where they last logged out (it's walled in or lost in the despawning)