If you pay over $200 on a PC, then your not growing mushrooms. As you can get a viable 21quart 15psi one for less than $100. You just have to look around. Also, BRF cakes do
not need to be PCed... Just steam them for an hour(1/2) or so, put a layer of verm on the bottom, as well as; on the top, as this will help with the excess moisture in the jars. Using kits can be a pain, as they usually give you everything at once, and expect you to do it. Although there are "teks' on the net for using them, you'll find it MUCH simpler to buy: quart jars, a PC, WBS, vermiculite, perlite (not even really needed), a tub (or two), a pan, tin foil, and then purchase your spores.... All that would cost $150~ and you won't need to spend any more, maybe $10-20 here and there... and if your going the BRF way, exchange the quart jars for pints, and WBS for organic brown rice flour.... pretty simple.
As for the topic at hand: No, these things don't expire. I imagine you could mean the "pre-sterilized jars"... well, they ARE best used asap, to prevent contams.... and I've never "waited" with innocing my jars longer than a day or three.... so I can't rightfully comment on this part. Although a simple steam bath/PC will cure that ailment in an hour or two tops.
01:13:08 ‹Ellis DEmpty› I met the people living in my head... I disturbed them while they were sitting down at the table.... They were as shocked as I was!
We were born too soon to explore the cosmos, and to late to explore the earth. Our frontier is the human mind; religion is the ocean we must cross.