I read a lot of comments about putting some sort of screen cover over the appliance vents to keep wasps, daubers, etc. from clogging up the works, but I'm wondering if folks cover all of them? I can seen covering the large furnace vent openings. The refrigerator's compartment doesn't seem to have places they could get into and clog up. And the water heater already has a screen over it, -not real small, but it seems small enough to keep wasps out. In a lot of years of trailer camping, I've not had any trouble with critters getting in to these things, but I'm wondering. Advice?