lol so use malt.. gotcha
The grains weren't sealed but they were in a plastic bag after being crushed then tied shut. So there was some air inside the bag but it tied tight enough that it wasn't allowing air to come in( unless there are super small hole in the plastic bag). I could squeeze the back and it wouldn't deflate or anything...
Would stale grains just taste hard?
Honestly I have 3 extract well 2 kits that are now months old. the 3rd I recently brewed, and one of the 3 is over a year (I don't remember which). Stored in the mostly dark basment, but summer temps in the 70's. The wort seemed ok, as did the grains. The yeast was dry and fridged, but I did a starter, inpart because of my new stir plate.
Anyhow. These were shiped by Austin Homebrew. the DME looked like it came from LD carlson that way. As far as going stale, it is a function of airflow. These even without the air vacuumed out didn't have fresh air being brought in. The hops were in the standard vaccum foil bags.
I plan on bottling this weekend, I'll let you know. I'm not recommending this for everyone. I may have had a few points of quality decrease by not using freshest ingredients, or I might not. I'd not be surprised to find out that you can store the product for a couple of years before use. It is a matter of how it is stored.
Anyhow OP, let your tastebuds tell you. I bet stale grain is going to taste 'flat' and not 'vibrant' (as if those descriptors help.) Non of my stuff reminded me of food that had gone stale.
At this point since you've paid for the product, worst you could do is waste time attempting the beer, but you might find it is passable.