Freshness of Potting Mix.

[peeweelovesbooks]

So. I was cleaning out my orchid supply area. I keep my potting mixes inside a large plastic tub, which was supposedly airtight. I noticed that the clear bags in which the orchid mixes come in were humid. I opened some and they smelled musty.

I decided to throw them away 1) because I wasn't sure they were "good" and 2) I'm not planning on buying any more orchids of that type.

which, leads me to the question.....if you don't use a particular orchid mix immediately, how long do you keep it? How long are they good for? I'm sure the ingredients degrade or start to at some point, but how to determine that? I know lava rock lasts forever, but what about other ingredients?

I erred in the side of caution, and well, like I said before, I'm not going to buy any more orchids of that type, but I'm curious as to what everyone thinks.