"Balderdash" wrote in message
ups.com...
I have several mouse traps around the house. I've noticed that a few
of them have snapped and there is nothing in them. Both that snapped
have been there for about 1 month. Will mouse traps let go by
themselves after a lenghty period of time if they don't catch
anything.

Clever mice? Roaches?

Depending on the method of trip, thermal cycles which cause expansion and
contraction could cause tripping without the help of a critter.