I've never had much frost build up, but I've never lagered that cold for more then a week or two. I usually unplug the freezer and leave the lid open for a few hours (it's in my garage), then come back and wipe it down real good, go back over it with a mild disinfectant cleaner, then wipe it down again with a damp paper towel. Never had mildew, or smells build up. Been doing this for a little over a year now. I leave it unplugged with the lid open when I'm not using it.