The answer for your question would be to ask once. if not done put in time out. I waited too long to discipline. The longer I waited the more the anger build. If I cut it right off at the beginning I am sure to get better results.
I have the same problem with my children. I think there are two issues at play here:
1) The children's behavior: Im not sure timeout is the right answer. Ive never found timeout to be an effective punishment, but thats just me. Ive found that long term behavioral change comes more easily from reinforcing positives vs punishing negatives. On top of that, what are they learning about from timeout? Especially if you are in a rush, youre only hurting yourself.
How about you adopt a reward system? Or instead, start getting ready earlier? Or count how many times you need to ask things and make a chart to show them their growth?
2) your behavior/attitude: how can you prevent yourself from blowing a gasket? How can you remain patient and/or calm? How can you maintain an even voice level?
Just my opinions though. Im by no means a child psychologist.
