Another thing, most of the AA's I've used (standard, maybe rechargeable are different), the wrap is done at the factory and it's a tougher metallic wrap. Different material and it's not just heat shrunk, it's more like an adhesive so it sticks much better. As others pointed out, 18650's weren't designed to be external batteries to swap out.
If your wraps are getting chewed up, maybe it's your mod? Some use those flat prong style contacts (not sure the proper name). They tend to be battery rippers. Others that use rounded spring loaded contacts don't seem to be as rough on batteries. I had one I tore that was my fault, the spring loaded contact in the charger slipped and raked the battery. I didn't have it seated well enough. Outside of that I haven't had to rewrap any batteries in months, like 4, 5, 6 mo. I swap mine out daily so they see plenty of action. The wraps are pretty damn thin though. Personally I avoid mods with those tab style contacts, guess I've gotten lucky. None of the few mods I own are too tight for the batteries.
