"I respect your opinion"
In metal I would say 7+ is long, 5-7 is average, 4mins or under I would think short. For rock, 3-4mins is much more common, and for older songs (the Beatles for instance) 2minutes is probably long
Songs that are five minutes or under are definitely short, with seven to 10 minutes being average.
7-10 is the average for prog, definitely not incredibly short.