I flew nights-only for 30 years and found it infinitely preferable and better for my health than the couple of years prior to that when I flew the usual kind of 4/2/4/2 mixed earlies / lates roster. Horses for courses, etc, but for me, the killer was always four successive 05.30 starts after a restless and shallow night's sleep as I was always afraid that the much needed deep sleep would cause me to oversleep and then miss the 05.00 to 05.20 Report Time.
And, of course, as most short-haul freight operations shut down for 36 hours or so between Saturday am and Sunday pm, I reckon work free weekends were always more plentiful than if I'd been flying people around rather than boxes.