I keep traps set for mice all the time... and rat traps, and larger traps for stoats or anything that size thats by the hen house, and in winter, a fox trap. I have caught mice (many!) a few rats (not in the last couple of years) and three ferrel ferrets. I think its best to keep on top of vermin, rather than waiting for there to be a problem, takes seconds to check the traps every day.
Also caught the cat a few times and dog once