UPS schedules can be challenging to maintain a healthy circadian rhythm. That was my #1 concern when deciding to accept a job here. I fly international 747 and have found, if I make it a priority, I can maintain a reasonable circadian rhythm. There are a ton of variables that will affect your schedule at UPS. Be flexible, figure out what you can handle and chase that lifestyle/schedule.

Some things I've done to maintain a healthy circadian rhythm at UPS:

I try to stay on Home time for my rhythm (eat, sleep, poop) even while traveling overseas. This won't work perfectly, but if you stay relatively close, it's easier on your body and easier to readjust when you get home.
Boiler said best earlier, make your health a priority when working (eating healthy, sleeping and getting a workout in) and it'll pay-off. There's food everywhere on these trips-just say no
If you treat every trip like a party, drinking and eating everything in sight, it'll catch up to you.
Nap, Nap, Nap, when able. Big benefit of the 74 lifestyle. A 3-4hr nap will do you wonders on an all-nighter.
Trade or post trips with show times that aren't favorable.
Alcohol is not your friend, it destroys your sleep quality and your health. If you wanna drink, do it at home and not on the road.

Having said all this, I've found this lifestyle to be very agreeable, although it takes some effort to make it so. I can't say this loud enough, LIVE IN DOMECILE if at all able. This alone will forgive 80% of the sins of this lifestyle.

Cheers-N48