I mean places like UPS already have 24 hour operations in a sense aka truckers/pilots and engineers (train driver) are always working. Their major hubs are sorting packages 24/7 as well. Local hub sorters aka mostly the guys that pack trucks and actual delivery guys don't work 24/7 most because it would not make any sense to do so.

Now you want to know who really should work more hours and better yet harder USPS. Also have them cut out the BS federal holidays like Columbus day aka only USPS takes them off everyone else worked.