Every time I flush the engine and change the antifreeze I pop the thermostat. Last time I did three of ours in the same day. Can be a bear if someone played Godzilla on the bolt in the past or hasn't been off in fourteen years. Is no need for the bolt to be any tighter than a spark plug or oil filter since the sealing is by an O-ring. Bolt just holds in place, does nothing to stop leaks.
Secret is to clean the mating surfaces rigorously and to remove/replace the housing smoothly. If the housing sticks after removing the bolt I put the butt end of a long screwdriver into the housing and use that to rotate the housing out..
To replace, I seat the housing first again with a long screwdriver on each side, then add the bolt to hold it down. If everything is clean and lubricated, it just slides into place.
I replace the O-ring every time (99 cents at Pep Boyz, grab a few) and lube with anti-seize, lower gasket was just added because of a few complaints of insufficient heat and does nothing to stop leaks.