You apparently don't work in such an area. If you've got 15 routes, and only 3 are in town, everything else runs 200-300 miles a day, or more, you don't send the part timers out then the fulltime later. Fulltimers will start early, run all day. In bigger cities where more rts are in town you'll see the early part-time thing, but extended rts will still run all day with one courier. Part-timers aren't going to run to spread out areas 70+ miles from the station, do P1, then run back to hand off vans to FTers who'll then drive out into same areas for P2 and pickups.