> I boil corks and use them immediately.

Murray,
Boiling corks may actually harden them prematurely; just spritzing them
with sulfite seems effective for me. I keep a spray bottle premixed
with a 1% solution of sulfite on hand for this among other things. I
keep corks in the original bag and keep them tightly closed, I have
stored corks for 2 to 3 years before getting through all of them with
no ill effects.

Joe