I have a crapload of old grain left over from the last bulk buy I did when I was brewing a lot. This is 4yo grain, I believe. I had brewed a few batches with it early last year Jan/Feb. One of the beers, I felt, came out very good, one was meh. It was with a completely new system, new water, new recipes, new everything, so i really couldn't say it was the grain or not, especially since one beer was very nice.
Rather than throw out 100+ pounds of grain, I figured I should at least try to prove whether or not it's still fine of brewing (FYI, the raw grain flavor and texture, to me, is no different than 'fresh' grain). So, I now have ingredients to brew two batches of session IPA, one with old grain one with new grain. Not the best style for comparing grain, to be sure, but session IPA was next on the list.
I don't really have much attachment to the grain, I almost chucked it a few times already considering I didn't know when I'd ever use it, but didn't have a good place to throw it away. I figure if it's useable, now, might as well use it.