Jess, they're substantially chewier than rolled oats. A bit like brown rice, actually. My package says 25 to 30 minutes. It usually takes longer than that. I cook it on low or very low heat until almost all the liquid is absorbed.
(Added advantage, you see, of not having to clean denatured oat protein and other goo off the entire pot.)

I'd say reheat them on the stovetop with a little water.
Today's batch was slightly wet--I had just under three cups of oats left in the container. Time to get more!