Fagvirgil and Cliff Secord have given you a good overview of a long-distance cargo pilot.
I'm retired now' but pushed a C5 and 747 thru the skies for 37 yrs --- 90% of the flights were over the Pacific, North Atlantic, or to South America.
Almost all my flights were with a 3rd pilot, or double crew (4 pilots). On a typical 747-400 flight from ORD to NRT (about 12-13 hours) with 4 pilots, we would split the duty and have a "shift change" over Alaska (6 hrs each). Samo, samo on 14-15 hr flights from LAX to SYD (or HKG), shift change at halfway point.
To while away the hours in the seat while boring a hole thru the sky, I would read --- same on 1-5 day layovers in some hotel. Always carried 5-6 books on each 14 day sequence.
Never flew pax, but we would dress up and look spiffy like an airline pilot from hotel to plane, vice versa. Once on the plane, uniform would come off, replaced by sweat pants/shirts and, for me, bedroom slippers. Before landing, we would re-dress and look professional again.
Don't know if the above has changed much, but that is how was for me for 37 yrs.
Best wishes for a rewarding flying career