This week I finally got around to using the two sheets I coated back at the end of June. The boards have been stored inside in my back room. Even with the AC going it usually gets a bit over 80 back there this time of year so that probably plays a big roll in this but....
I found that the coated board had turned considerably yellower than it was immediately after coating/drying. Doesn't really bother me since I plan on painting but I was still a but surprised at just how yellow the board got.
The other thing I discovered is that after sitting for a month and a half the boards warped somewhat away from the coated side. (so the coated side was convex and the uncoated side was concave.) Again not enough to make the boards unusable but considerably more warped than uncoated boards from the same batch and they were not warped when I initially coated them. I'm guessing the heat in the back room is a big culprit here.
I just picked up another half dozen sheets today and after making sure to pick the flattest ones in the store when I got home I had to ask myself why I bothered as the ride home in my truck in our AZ heat left the boards as warped as the worst of the ones at the store

Still usable but don't think I'll waste so much time trying to pick the flattest ones this time of year
Going to try and coat these both sides to see if that helps keep the flatter. The ones I did in June I only coated one side since I was still experimenting.
Coating right now is kind of tricky...gotta do it outside since even outside this minwax gives me a nasty headache. But it's over 100 in the shade still and even after dark it's over 90. So by the time I get a whole board coated the minwax on the first bits is already dry enough that I can't wipe off any excess
