I recently found this sub and wanted to share my experiences. About 15 years ago I used to work for a corporate electronics retail giant. At the time I was hired as a 'stock boy' to help manage inventory. It was supposed to be a temporary position but ended up turning into a sales role once they saw how well I interacted with customers.
After a short time I was promoted to an “assistant manager” at a second location within the same mall. I was naive and young and stupid at first and just kept thinking how this would look on a resume being promoted so quickly! I was expected to come in early and stay late but was only paid for my regular shift. I didn't question it at first. Figured it was part of being manager. After doing plenty of favors like covering managers shifts from time to time, to helping with the main stores inventory, even though I wasn't on that stores payroll, to being asked to help another store with their inventory after a break in at like midnight, my final straw was also a huge epiphany for me.
Eventually they closed the second location I was at and moved everyone back to the main location.
The day I quit, there was a nasty snow storm, the buses weren't even running it was so bad, I woke up with the flu but it was my day to open so I called a cab and went in early just to ensure I'd actually make it on time. I got to work and opened as usual. Over half the stores in the mall weren't even open because of the weather. The mall admins were even considering closing the whole mall because of it. 2 hours into my shift and it's still dead. Not one customer and still half the mall closed. I could barely stand I was so weak and drained. I called my manager who was scheduled for the afternoon and asked them to come early because I had to leave as I was sick. My manager's response was that the weather was too bad for her to come in and that since I was already there I should cover her shift. She lived closer to the mall than I did. That was it. I said “You need to come in now because I quit.”. I hung up closed the doors and went home.
Don't do favors for your employers, you'll never get the time back you spent on them nor will you be guaranteed they will ever be repaid. Just don't.