Hi Linc,
Welcome to the Heartland Owners Forum and family. We have a great bunch of folks here with lots of information and all willing to share their knowledge when needed.
I live in South Texas, I have never had a problem with mice and critters. The unit is parked next to our house under a cover, and we do have an outside cat, (now 2 and some wild ones). We do keep the house and outside sprayed for bugs and stuff. A lot of folks do use the dryer sheets and some other things to help keep the mice out, but we live in the South and are in and out of our unit all the time. It's not like we close it up for 6 months till the snow melts and all this time the critters and mice are looking for a place to stay.
So,,, what you need to do is get your Road Warrior ready and hit the road.. travel to the South... Texas... in the winter and go back in the summer.
I'm sure you will get some more suggestions from our other family members soon.
Enjoy the forum and your new toy.
Jim M