One of my grandparents had surgery so I stayed at the Hospital with them overnight. It was a small facility though so I ended up in the most uncomfortable chair ever. It was also freezing. I got NO sleep for 2 days.
Went I finally got home I was GONE. I woke up to realize I had missed a full day.
Ive slept like 12 hours without waking up before.
If I get to much sleep then I end up feeling more tired when I do wake up.
So, I usually set a alarm unless I forget so I don't end up sleeping for long amounts of time.
If I get anything below 5 hours though then I am gone for the day and I enter zombie mode.