How long crush grain can be stored before it's no good ?

I would dump it and fork over the $10-15 to buy new grains. Hefeweizen is about the cheapest beer (ingredient wise) to make.

 

Brew it, feed the spent grain to the pigs and decide who got the better deal

 

I'd brew it...as long as you have stored the grains well. Now if they were in a paper bag in the corner of your brewhouse for that long, I would think about buying new grains. Food grade buckets are less than $5 at WalMart and are well worth it for keeping grains in until you brew, especially if you get them ground at your LHBS or online.

 

I have used 6 month old crushed grains and liked the beer. It's going to depend on storage, and perhaps how sensitive your palate is? Just because I liked the beer I brewed doesn't mean it couldn't have been better if the ingredients were fresher.

What about the yeast? I wouldn't use 7 month old liquid yeast. And I wouldn't use dry yeast for a hefe because I had a bad experience with dry yeast and hefeweizen. Fermentis WB-6 -- turned into a clove bomb with no characteristic fruit to balance.

@Supergenious has a valid point -- the ingredient cost here is small, the commitment to brew a beer is many hours. Is it worth many hours of your time to brew a beer that might be so-so because you were too thrifty with your ingredients? You are not starting out with the best of chances for making a great beer.

 

I'd recommend tasting the grains first. If they are mushy/chewy ("slack" is the proper term) or taste stale, don't use them.

Some people will say crushed grains are good for many months or years. Some maltsters will even say it on their web sites. I say that if storage conditions were as good as possible, old crushed grains could be okay, but not ideal.

I crush my grains right before dough-in.

 

Pigs love Hefes.

OP: Brew it.