Take it off at the end of the season. If you leave it on too long it leaves a residue. I fractured my heel and ankle a couple of years ago and after 3 months of being in the house I had to get out in the woods so I wrapped my crutches, cane and rifle in the stuff. I took it off my rifle after a couple of months but I left it on my crutches and cane for bow hunting and by spring when I took it off of them I had to do a little cleaning to get it all off.
Now, keep in mind that what was on the crutches and cane saw a LOT harder use than what it ever would on a gun so that might make some difference. When I got to a hill I couldn't walk up it because my ankle wouldn't bend so I would crawl and drag everything else with me. One afternoon I crawled about 100 yards through the mud to get up a hill to shoot a deer and everything was covered with mud by the time I made it. So, yeah, it is pretty tough stuff.