Grain: how old is too old?

Mashing
1

I just discovered a bag of mixed grain I crushed 5 or so months ago for a batch, and then never got around to brewing. It’s been stored in a cool, dry dark place, but 5 months is a long time.

What do you think? Toss it? Or might it still be used to brew a good beer?

2

Was it in an airtight container?

Either way you could try to brew with it expecting lower efficiency and have some dme on hand if the OG is too low.

3

Taste it. If it tastes stale or chewy, get rid of it. If it tastes fresh and crunchy, you’re good.