I've found that cooked oatmeal freezes pretty well. I like to make Pumpkin Oatmeal
and then I freeze individual portions and reheat later.
How long have they been sealed up in the Foodsaver bags? That should buy you a little extra time if they've been vacuum-sealed for a while. (And it's good for keeping the bugs at bay.) So you might not have to use it all as quickly as you think.
You can also use ground-up oatmeal as a thickener instead of flour or cornstarch. Just grind it until it looks like flour.