Y'all... traveling with 3 H bags for a 26-hour flight was HELL.
A few points to consider:
1) If you expect to place your bag in a hard shell in the overhead bin, be prepared for the possibility that the gate agents may make you check your bag anyway due to the compartments being already full. So, fly business or first, or get in line very early to avoid this. Or, prep your bag as if it might undergo the violent tumults down in cargo.
2) If you must use the overhead bin, be prepared that passengers may move your bag around and it won't be in the same position as it started. If you're smart and use a dustbag to protect and conceal your bag, then the other passengers have even less of a clue that they need to care about your stuff. Overhead bins otherwise aren't terrible IMO. My bags were fine, esp compared to the annoyance of keeping a bag below the seat in front of you.
3) Even if you put your H bag in another tote and put it on the floor below the seat in front of you, eating will be hard and you'll be paranoid about food dropping on it.
4) It's really hard to pack snacks, hand sanitizer, or anything else that could leak on or stain your bag. Especially for long-haul flights.
5) If you put your bag into a tote, be mindful of anything within or in/around the tote that could scratch your bag. There may be a fair bit of friction between the tote and your H bag as you move it around, drag the tote to get things from your bag, run to your next terminal to catch your next leg, etc.
6) Make sure the tote in which you put your bag is waterproof--even if you don't spill anything, the passenger next to you might, or the flight attendant could.
7) When placing your H bag into a dustbag, it helps knowing on which side your turnlock sits. Bags going through customs or security can have rather precipitous drops that do not do them any favors. Same with turbulence if they're in the overhead bin.
8) Packing H bags in a suitcase means one is relegated to that bag ONLY having clothes. Anything hard, sharp, damp, or heavy brings about way too much concern for damage.
9) If you have a very tight connection in a crowded airport like LHR, there's a good chance your bags aren't gonna arrive until the next day or even later, depending on crowds and flight schedules. Airtags do genuinely help and I was surprised that BA actually put their own zip ties on our bags (which did arrive late but whole, in one piece, with everything in it... including rather expensive electronics).
10) Try not to sit next to kids or have your own kids sitting next to you with an H bag underneath, particularly for long-haul flights. It's... stressful.
11) Check customs, esp if you have multiple H bags on you. Some have limitations on personal use, and one is either stuck with declaring and paying heavy "import duties" or holding bated breath that the officer is too busy looking for gold and electronics to care about your vintage bags. I was really surprised that even though our bags were stuck in another airport without us, customs STILL grilled us about the total value of what we were bringing in.
I know theft seems to be the most obvious concern, but I completely underestimated the endless possibilities for damage. I'd say traveling with a luxury handbag is easiest for flights with just one leg under 5 hours, and all the better if one is in business or first.