We have some regular Samsonite hard shells that have done fine over the years when we need to check baggage. Had two of them for nearly 20 years and plenty of trips. One of them survived coming off a car roof rack at 80mph on a wet windy night. Found it in a field, just a few more scuffs. Dunno about the TSA locks on my old ones, I go to Europe via Asia these days to avoid that stuff. Must be a system for the new ones.
I can do 3-4 nights business trip with a carry on bag (I prefer a shoulder pack to the wheelie ones, easier to get stuff out of in mid flight). I have a hunch that a backpack gets more interest from security and service types.
Some of you may remember Alan Whicker, glove-trotting journalist from he 60s. His motto which I try to stick by: take half as much stuff and twice as much money.
Long haul, pick your airline carefully. Seat pitch is important. Who are you flying with Bob?
Agree with zenheretic's advice though I have a different view about shoes. I wear a decent pair of shoes and keep them on till we're well clear of the ground. I don't want to be involved in an evacuation in stocking feet. I stick some sockettes on once we're under way, usually slip my shoes back on when going to the toilet (some arlines don't keep an eye on the state of the floor there

). Otherwise, go easy on the food and alcohol, sleep when they turn the lights out, have a great time in Aus.