What
@camonick said.
I’m a grain farmer, and I’ve lost track of the times I’ve pointed this out, but the “fresh” grain that you’re paying top dollar for might be going on 2 years old when it arrives in your hot little hands. And, cereal grains are exposed to 02 throughout the entire cycle of planting, growing, harvesting, transporting, and storing. Oxygen is part of that whole photosynthesis thing.
The malting process removes almost all of the moisture from the grain. A bushel of barley has a standard test weight of 48 lbs. Most malting varities are closer to 50-52 lbs. After malting, the malted grain only weighs 42-44 lbs. Barley is traded by the hundredweight, that is, so many dollars per hundred pounds, so the maltsters are only selling about 80 lbs of malt for every 100 lbs of barley they pay for; the difference is turned into steam. If you ever pass by a malting facility when a batch is being kilned you won’t be able to ignore the massive clouds of steam going into the sky. The point of explaining all of this is to emphasize that malted grain is as dry as dry can be, and if it’s kept that way, will be suitable for brewing almost indefinitely. Yes, the maltsters will recommend using the malt within 12-18 months, or whatever, but they need to do two things. 1. Cover their ass because some folks won’t be particularly diligent about keeping grain sealed up and dry, so there must be an “I told you so” to back up their advice, and, 2. Sell more malt.
All of that said, I wouldn’t suggest that one should simply disregard the age of their stored grains and not do a FIFO inventory management. But, I wouldn’t toss old grains that I was sure had been kept cool, dry, and free of tiny livestock. I can say, based on a working lifetime of experience with stored grain, and depending on it for my livelihood, that grain ages a lot better than the conventional, message board, wisdom says it does.