I think I've seen a post before on this subject, but I can't find it. Once you have mixed up cake batter, how long can you keep it before using it? Can it sit on the counter for a few hours or can it be refrigerated? Does it make a difference if it's a cake mix or from scratch?
My own experience has been that if I let the batter set long at all, it doesn't rise will. The faster I get my batter to the oven the better it typically does. Hope this helps!
The longest I have keep batter has been overnight in the frig. I typically use a box mix and embelish it with other ingredients, which includes baking powder. I have not had any problems with the cakes rising.