As for "glue" or vulcanizing fluid - I tried buying that in bulk, and
it
definitely did NOT have shelf life. Now I go to a dept. store and buy
the cheapest patch kits I can, about $1.50, pitch the patches and use
the glue. I think I'm still far ahead overall in the cost of patching
supplies.

give 'rubber cement', the paper stuff, a try. i was fooling around
& made a 1-in x 3-in patch using an old inner tube, rubber cement &
naptha/Coleman fuel (as a liquid buffer) and lived to tell about it. i
had a tube with a 2 in split and wondered if it would work.
if i'm DIY a patch from an inner tube, i'll coat both surfaces with
the rubber cement after a naptha cleaning & allow both surfaces to
_dry_ (NO CHEATING!)