Just because you can do something doesn't mean you should. It is a risk versus cost thing. Whenever i rebuild any of my motorcycles i alwlays use new copper sealing washers on the head bolts. Sure, it will probably seal OK a second time, but if it doesn't, it means pulling the engine again. I just bought a used 1977 Kawasaki 200, and I changed the oil but didn't replace the o-ring on the drain plug, Now it is leaking on my driveway. Not a big deal, but replacing the .50 o-ring would have saved me some hassle. some guys refill small 1 lb propane cannisters. Some of the dad's in my son's Boy Scout troop were doing this, but I refused. All it would take is one can leaking and some scout get hurt due to it, to save 5.00. And this troop has some money, most of the dad's are high tech engineers.
Don't get me wrong, I am not some safety nazi. I fill my own cannisters if they look real good, and I have popped out hundreds of pre-installed primers just to use them again, and they have always worked. Just wouldn't do it for ammo that I really depended on, just in case.
Funny, my Mom always used paraffin for a lid when she made jam. One year she made 40 jars from our 2 plum trees. She didn't really like doing this kind of stuff, even though she grew up on a farm. She said she wasn't buying any more jam until the plum was all gone, and it took almost 2 years for us 4 to finish it off. I still don't ever buy plum jam.