I have an acquaintance who was given some dried shrooms (pscilosibin (sp) I presume) a good 2 years ago at least.

Assuming they were properly dried and kept in a plastic bag, do they have a definitive shelf life? He's worried about getting poisoned. Of course I don't advocate him using or possessing such things, but I figure if he insists on it, he ought to know if they 'go bad.'

Not poisoned.. but if they were just in plastic bag i would super guess there is no psilo left in them. also smell, i have a bad nose but i can always pick out a moldy shroom from a good one. (sometimes you cant see it)

i would go through them one by one to see if there is any left

is there a preferred way to store them after drying?

L&G!!

After completely drying, the way i have always heard and will be using soon, is in a mason jar filled with co2 (food grade dry ice) then in the freezer

Dry them, throw them in the blender, stuff them in capsules, and then put them in the freezer. It'll last for many years. Keep a spore print someplace safe and you'll be good for life. That's what's great about shrooms, they can NEVER take them away from us.

When you put them in a jar filled with CO2 it is not even necessary to freeze them. A dark cool spot will do just fine.

Peace

If they were fresh when properly dried, and have been dry since, then you dont have to worry about live bacteria or toxins produced by bacteria.
Also, i dont think some sort of chemical decay of those psilocybe mushrooms has produced toxins.

I say you dont have to worry about getting poisoned when eating those mushrooms.

I have read somewhere that liberty caps (mainly contains psilocybin) can be stored in plastic bags on a shelf for years
with minimal loss of psilocybin.

Cant find the source tough, all my books are in my mothers attic.

I made a purchase in bulk several years ago that lasted for 3 years (until gone) in plastic bags without noticeable drop in potency (P. cubes).

Keep them ultradry in a desiccator with calcium chloride or sodium hydroxide.
A well closed container with drying agent and pre-dried mushrooms with precautions taken to prevent they can touch. A large ziplock bag with open jars of mushrooms and desiccant inside is also fine. Moisture is your worst enemy!

Calcium chloride is sold as 'Vochtvreter' in Holland, elsewhere it's 'Damprid' I think. Sodium hydroxide is very hygroscopic too, but I wouldn't like to store edibles above it, and you can't fill the jar with CO2, this will react with the lye immediately.

I'd be very hesitant to have lye in such close proximity to something i'm going to be ingesting...but that's just me. Also, there should be no reason you should have to use desiccant + CO2, as once the shrooms are dried with dessicant, no more is needed and the desiccant can be removed. Then CO2 can be added and the jar sealed/stored in a cool, drak place.

herrrmmmmnnn..... are you aware that solidified CO2(dry ice) expands rapidly apon warming(returning to its liquid/gas state) increasing the pressure inside a sealed container, so rapidly in fact that it will easily explode a sealed glass jar, even a small piece(of solid CO2) apon warming can build enough pressure to rupture even a high strength plastic bottle...

if one does feel inclined to use this method of storage, do be sure you immediately take the lid off as you remove your container from its icy slumber in the freezer, to release the pressure, lest you injure yourself...

even in a dark cool spot it will warm and build pressure, slowly mind you, it might take a day or two before it explodes...

honestly unless im missing some key point, i think this is a very dangerous idea and not practical, please correct me if im wrong.....

That's me too. I certainly wouldn't use the crappy setup above with Lye

I don't bother with CO2 because every time the container is opened, some air and moisture may leak in and I start to worry if the CO2 is really still in there.
Water is a catalyst for many, many chemical reactions, if the mushrooms are bone dry not much will happen, oxygen or not. Sulfuric acid or phosphor pentoxide would make it even drier, but that's a little over the top

It's all a bit paranoid, if stored reasonably dry in a normal climate without special precautions they stay well very long, months or even years. But why not play on the safe side and keep them ultra-dry and/or oxygen-free, it's cheap and simple.

BTW, I use my computer exhaust to pre-dry them

Yes, good point and thanks. If using this dry ice method, don't close the lid until all CO2 has evaporated and the jar is at room temp!

dryrite (calcium sulfate) and reduced pressure. don't even need to purge with inert gas

^^ I bow to you, that will keep them well for thousands of years. Do you store them in liquid helium?

no
not even kept in the freezer.
psilocybin is stable at RT.
they just need to stay dry

Benzyme, what is that you have them in? I'm assuming that it's some apparatus to reduce pressure, but what is it?

vacuum desiccator