Yeah, I wouldn't be very excited about flying a Fedex or UPS feeder route just because of all the waiting. But I do know in some circumstances, it's not too bad. For example... I know of a freight op in Wisconsin, you show up at 7:30pm fly out at 8:30, get to your destination by 9:15pm, sleep at a company crash house, get up at 6am, depart by 7am, arrive at 7:45, home by 8:30am, and since you slept all night, you pretty much have the whole day to yourself.
Not quite as nice, but not bad, a UPS route in Texas with a different company. Show up at 9am, depart by 9:30. Arrive by 10am, and go sit at a company apartment that is fully furnished with cable and internet. 5pm head back to airport, depart by 5:30, arrive 6pm, home by 7:30pm.
I'm a bit hesitant to fly these kind of routes, because of all the waiting involved, but in some cases, they don't seem too bad.