We leave our Hawk on the Tundra full time. We've had it 4 years now and spend at least 30 nights a year in it. Aside from camping, it's great to have to be able to haul along a place that you can stop and fix an impromptu picnic, or have your own porta-potti and a place to use it. We go snow shoeing in the winter and will sit in the camper with the furnace on after, sipping on hot chocolate to warm up as well. I've found that leaving it on just opens up a few more options and possibilities for uses of the camper.
As far as resale goes, I figure if we amortize the cost over the years of use we get, and the enjoyment we get out of it, it has more than paid for itself. When we do get around to selling it, I'm sure it's residual value will be far better than pretty much any other regular camper or trailer out there (though that is not why we bough it).