I took the Greyhound from Sault Ste. Marie to Kenora, Ontario to fulfil a contract, during an Air Canada Strike around 1999. It was about 15 hours, from midnight to early afternoon. There's no middle armrest, and for the first three hours I sat beside a teenage girl. As the bus raced around the curves of the Lake Superior Highlands, passing everything in sight, we were continually jostled against each other. She got off at Wawa and for the next 12 hours I had the two seats to myself and managed to sleep much of the night. I even slept through the bus getting pulled over and one of our passengers getting arrested just after White River (original home of Winnie the Pooh...ask me about that) after he shoplifted at the rest stop. I hardly ate or drank, and didn't pee for almost the entire trip.
There was nobody horrible near me, but more than one of the passengers was on a multiday trip across Canada, freshening up in rest stops along the way.