I don't have any crazy stories. Probably the fastest I've ever covered a level range was from 40-51 on my BRD over the course of 3 days.

I've leveled many jobs from 1-10 in a matter of hours.

I've managed to get 8 merits (80k XP) in a PT that was just short of 5 hours long.

I once leveled 5 jobs from 10-20 in a week.

Nothing as impressive as some of the other sprees here >.>