How long can Hermit crabs live without food?
1 month
Another view: I honestly don't know how long they can live, but
they can easily return to a tank that is not kept clean. Try to
figure out what attracted the mites to your tank in the first
place, and correct that so it won't happen again. Mites can be
extremely painful and dangerous for your crabs. A good ocean-salt
bath will kill the mites on your crabs (make sure it is an approved
ocean salt, not table salt or sea-salt meant for humans, which is
deadly to hermit crabs because of additives). Follow this link to
get excellent information on getting rid of mites and keeping them
out of your crabitat: