Once in YUL on a YYZ-PHL-YYZ day trip.
Snow storm in PHL cancelled my PHL-YYZ leg. Needed to get back so I could go to MCO the next day with family. Only alternative was PHL-YUL-YYZ so off I went. Arrived about 6 hours late in YUL (~2 am), slept in airport so I could line up first thing in the morning for YUL-YYZ. Turns out they were all cancelled the next day because of the same storm!
Ended up YUL-PHL-YYZ in the end, so I did YYZ-PHL-YUL-PHL-YYZ in 36 hours. Didn't get miles because I did not know about FT at the time! Our MCO trip was actually delayed 24 hours due to the storm! I should have stayed in PHL!!!
Sleeping in YUL was simply a miserable experience. People walking by all the time, announcements, lights on...