lots of smaller er's that see <15k pts/yr have 24 or even 48 hr shifts. at one of my current jobs I do 16 hr shifts and some other folks do 20 hr shifts.
typically you have a call room right off the er to sleep, take a shower, eat, etc
lots of these jobs in the NE and upper midwest.
sweetest gig out there is the er on catalina island. 1 week long shifts. avg volume 1 pt/day. you only need to be available within 20 min which allows you to roam most of the island, play golf, etc they have 2 full time guys who alternate week on/week off and an rn who is physically in the dept 24/7.