Hermit Crab out of its shell

Question
My hermit crab is out of his shell and I don't have a new one to put in its cage.  How long can it survive outside of its shell?

Answer
Can you rinse out his old shell and place it back in there? Make sure you dont use tap water, it has to be dechlorinated if you use tap. You can also use bottled water.
I'd suggest getting a few more shells. They need a shell for protection and also so they don't dry out.