Mailing from coast-to-coast sounds like it would take a long time, but there are regular flights cross-country, and the sorting facilities bring mail to the middle of the coast, and then ship it straight across, east or west, depending. This means that the mail has to go first to a central sorting facility.
Truck and bus drivers must generally take a minimum of eight hours off between shifts, and their shift hours are often capped. Airline pilots are required to have 10 hours off between shifts to allow for transportation and rest time.
by law you should get a 15 min paid break every 4 hours. you should have a lunch break but they don't have to pay you for it. there are also laws about time needed off in between shifts if the shift is 12 hours or more. you should call the citizens advice.