I'd email her.
I dont' keep my JC stuff in the shower, but on the counter and on the counter in the bathroom it lasted a couple of years for me. I forgot I had it and went back to it and it was fine.
Now in the shower, in our humid state and my tiny closed shower.... no telling how long till mould.
Still that's weird since it must have preservatives in it.

I bet she'll fix you right up though!
2c/3a?
Low porosity, medium texture.
http://public.fotki.com/Medusahair/

If it smells good put it in your hair, if it tastes good spit it out!