For Mice Prevention I have done the following prior to storing Trailer for the winter and had no problems in 4 years (knock on wood):
* Take every food item out of the pantry and trailer. Don't want anything in there encouraging them and their friends to come in for.
* Clean the shelves down with a good cleaner.
* Purchase a few boxes of cedar moth balls and placed around each corner/vent in the trailer. Drug Mart has then. I opted for cedar as it smells a tad better than traditional moth balls.
* Purchased a few boxes of dryer sheets and layed those down all around the floor as well including storage bins.
* Last but not least since my trailer is stationary and I typically leave it plugged in all year I keep these devices plugged in and I think they help. they are plugged in 365 days a year. Only cost a few cents a month to run.
Bell & Howell 3-Pack Mini Pest Repellers - Walmart.com
All of these steps may be overboard but I rather go crazy with these steps then spend half my summary fixing wiring that the mice have chewed or replacing items the mice have destroyed. Rather spend a few hours of mice prevention then spend weeks/days fixing things in summary.
Hope this helps...