Shelf life for uncrushed grain?

I haven't been brewing as much as I use to and was wondering if my two row barley and other specialty grains are getting to old to use (12 months to 18 months old). I keep them in the garage in plastic storage bins with tight fiting lids and the specailty grains in 1 gal. zipp lock bags. I was buying in bulk (50 lb 2-row) to save some money. Will the malt ever go bad or effect the taste quality of the beer that I am producing?
Thanks, Dave

3 things you want to avoid when storing grains are heat moisture, and exposure to air. The bins are tightly fitting but is there a lot of air space in them? How hot did your garage get?
I left some specialty grains in my freezer for about 3 years. The ones that were sealed with most of the air removed were good and made good beer. I had one zip lock bag that wasn't tightly sealed and the grains were kinda soft and didn't taste fresh. I threw those in the trash.
I would say taste your grains and if they are crunchy and taste good go ahead and try a batch. If you do use them let us know how the beer turned out.
If you don't want to risk it, just replace the grain with fresh.

You're pushing the limits. Give some of the two-row a chew. The biggest problems will be the fats going rancid and the starches getting stale. Both will be obvious.