Dual o-ring seals for the win.
If you don't want to have to worry about floods anymore on a small light, look to the Photon Torpedo. Great backup light that good enough for a primary, for many.
I've had a UK light for nearly 20 years that still works like a champ. I also have two Light Cannons with nearly 100 dives on each that have been incredible.
Everyone's luck can vary. I do know that there are many, many dive ops in the Caribbean that have standardized on UK lights for their loaners. I can guarantee you they would not choose lights that fail regularly.
I've also had a couple of Princeton Tec lights that have flooded on a regular basis, and yet been replaced cheerfully each time.
So no, they're not perfect, but the bigger players (and some of the smaller ones) definitely recognize this fact and stand behind their products. Give them a shot, and try some different models until you find one that's a little more reliable than the ones you've tried to date.