put doner tank in freezer before refilling, a buddy does that helps
them to fill better.

i have reused some for other uses. left sit for a week with torch
valve open outside. a buddy suggested putting it on a vacuumn pump but
thats overkill if you asked me.

drilled out valve, puped with compressed air they can be handy for
clean ups, like bottled air.

added 2 to a small piston compressor for reserve capacity used for
many years. replaced with a rubber bladder i guess bigger HP
compressor that works better and weighs a fraction of the old one.

dont think in the box, the box isnt your friend.