Yes, a lot of people (on WTW) keep the jacks off except when they want to remove the camper from the truck.
If I removed my camper from the truck after every weekend trip I might want the jacks always on, to save installation/removal time, but not otherwise.
Yep, blocks, Lynx Levelers, etc, -- something under the truck tires -- is how I level the camper when camped.