How best to store grains

I've got a number of partially used bags of steeping grains lying around and was wondering how long they'll stay fresh for? I used them in a brew last week and am currently storing them in a ziplock bag in my cabinet.

I'm assuming they'll keep for at least a month or so, but would I be better off keeping them in the fridge? Is there an easy way to know if they've gotten stale/bad besides seeing strange things growing on them?

Take out a few grains and give them a munch. If they taste stale, replace them - otherwise you're good to go!

If they're already crushed get as much air out of the bag as you can and keep them cool and dry. You should be able to keep them for a month at least. If they aren't crushed, cool and dry they should keep for a year.