Triple miles really added up when you also got the 'elite' bonuses tacked on .....and so a 1K earned 425% of base miles....and since upgrading was relatively easy then, and the computer didn't always "check" to see if you were paid F, instead of upgraded F....
You would very often get class of service bonuses as well!!!
It made ORD-MKE mileage runs worthwhile!!
Best wishes.