If you use aluminum gas checks and the check oxidizes before you shoot the round, in my mind you waited entirely too long to load and shoot the bullets. I am not trying to be smart, I just know that aluminum oxides very slowly in most environments.
I would use the aluminum checks and never look back, were it me... If you happen to find a bullet with an obviously oxidized aluminum check on it, pull it off and re-check the bullet, or re-melt it. No harm, no foul.