Especially if you were in the Easter or Pacific time zone.
I lived in one of the few unique areas of the country where we were on Mountain time but got our TV from Central time zone stations, so Johnny Carson was on at 9:30 and Letterman at 10:30. But even with that earlier schedule, I would have had a hard time functioning at school the next day staying up until 11:30 each night to watch Letterman.