I don't know about preparing oats days in advance. It seems like they would get mushy but the idea of undercooking sounds interesting.

Like so many, I too get hungry after about 1 hour of eating oatmeal. I found if I add 1/2 of a chopped apple to the oatmeal, I'm ok for about 2 hours. Not much better.

For breakfast, this feels useless. By mid-morning I want something hearty like beans with chicken and salsa and tortillas. But for lunch, the oatmeal with apples seems to work just fine. My afternoon snack is more normal like fruit with nuts or seeds and its satisfying.