Most of the non union LTL companies give OT at different hours. Can't remember if ODFL is different by terminal or the same across the company. But you have some companies that give OT after 48 hrs some at 50 hrs some at 53 hrs some at 55 hrs.
However it is definitely worth it to join ODFL. You just won't get OT after 8 hrs everyday like the union carriers offer.