We had mice for the first time a couple of weeks ago. I’m not sure how long they were in there but I don’t think more than a few days. I had bounce sheets, cotton balls soaked in peppermint oil and Irish Spring soap graded up in plates all over our 5th wheel. There were droppings in the soap and some of the cotton balls were gone. I assumed to be used for nesting. I set 6 traps and got 3 mice the first time. Just got another the other day. Hopefully I got them all now. I’ll keep checking.
I agree with drsteve. Seal up all the holes and set traps. My RV is stored an hour away from home. I’ll take a drive every couple of weeks and check for mice.