I’ve slept in shelters often and have only rarely had problems with mice. Only a handfull of nights have the little buggers really been active. hang your food and anything that smells like it from a mouse hanger in the shelter. The mice don’t want you, they want your food. They usually won’t come near you, especially your head.
…of course there are exceptions to every mouse…
Point is, it ain’t that bad. Shelters are nice when you feel lazy. Someone else’s snoring is usually worse than any mouse. I never had any mouse damage the entire trail (or on any subsequent section hikes for that matter).
Anyway, yes, 0.5 mi is plenty. I’ve never seen a mouse run 0.5 mi and I would expect that mice, and especially shelter mice, would roam no further than 100 yard radius (seeing as they’ll get all of the scraps they need while they’re there. 0.5 mi should be plenty for mice, but watch out for the larger rodents (squirrels, raccoons, etc.) and mammals.
Have a fun hike. Try out a few shelters to find out for yourself.
-Howie
Hungry Howie