I ate the other half of the batch this morning, and it was just as good as yesterday. So sitting made in the fridge for 24 hours extra doesn't hurt it at all. In fact, I liked the walnuts better this time, they seemed more a part of the oatmeal than something just tossed on top.
This is good news, as I can make a larger batch (using a whole banana at once) and then divide it out each day.
Sure do wish I had saved more of it yesterday. I hope I can reproduce this and make it this well again. Mmmm.