Once a coworker of me was too slow for some 80+ y/o man when she packed her stuff in lunchtime. He snarled at her to hurry up. She calmly looked up to him "oh, you got a problem? I don't have a problem ... ah I understand, you're in a hurry, you still have to work, eh?" :D

I usually shop everything at once, I just avoid the rush hours. So I usually avoid shopping at Saturday at all (keep in mind that roughly 99% of stores are indeed closed at sundays and in pedestrian areas many shops will close at Saturday noon for the weekend) or if I have to buy something on a saturday, I'm in the store at 7am or so to avoid the crowds. And you are used to it anyway.