how long can you let cake batter sit? I bought some mini muffin pans to make tiny little cup cakes, but a batch of cake batter will probably take about 4 bakings. I have no intention of purchasing that many of these pans, I won't use them that often. So how long can I let things like cake & muffin batters sit before all the poof is out of the leavening & can I just add extra before I cook the later batches to make up for it? Or do I even need to?