I have extra batter...I covered it and put in the fridge...I vaguely remember someone saying that it can be used at a later time, but how long? a day? a couple of days?
I use my batter within a couple HOURS. Your cakes may not rise if you don't use it right away...But I'm interested to hear if anyone has a fix for this. I usually just pour the batter into a big pan, bake, cool and make cake balls out of it.
You can also freeze the batter in a zip lock if it will be longer till you can bake it.
I think cake mixes are more forgiving then scratch recipes. I've baked it a day or two later with no problems, after that I forget it is in there until I clean out the fridge. :-O
There is a thread on here that says you can freeze batter and it bakes just fine. Not sure of the details (whether scratch batter or box batter or how long).