So I had this mineralogy lab to do. 14 trays of minerals (50 each tray) that had to be described, identified, and tested with at least 5 tests that didn't include the standard scratch, hardness, etc.
It was at least a 24 hour-long lab. That's hours worked, not "wait 24 hours before eating solid food."
Unfortunately, I also had a final exam to study for. I didn't have enough time to do both, so my professor granted me an incomplete with the promise I would finish my lab during January term.
So I did. I paid extra for an earlier flight back, spent a week working on that verdamnt thing (turns out 24 hours was a conservative estimate), and triumphantly turned it in.
A month later I discovered that my professor doesn't count labs in calculating final grades. All that work (and money) and it doesn't fucking count!!