Many years ago, when I was young and single, I was staying at out-of-town relatives over Shabbos. I did some erev-Shabbos shopping for them, but as it was getting quite late I had to head to the checkout line before the entire shopping list was checked off. Since I was pretty sure the supermarket was open 24/7, I planned on returning motzei Shabbos and finishing up.
You can probably guess what happened next.
After getting confirmation that yes, the store was open the following night, I apologized again and made my way out.
Never.
Ever.