So my conclusion is that I need to drive the car more often. I typically take it out a couple of times a week but if I take it out more frequently, then the car is less hospitable for them.
Presently, the car is being serviced. They found a nest. The cost to demousify it is going to cost upwards of $1,000.
This past Winter, I moved my John Deere lawn tractor about every other day to avoid mice chewing up the wiring harness like they did last year. When I had it serviced last week for an annual tune-up, no evidence of mice was found.