I exchanged several 50 series plasmas with the issue you described so I'm aware what you mean. The bands were visible on static images as well as panning shots.
They were very annoying. I don't have the amount of hours you do and I'm hoping mine don't develop over time like yours have, as I don't even have the box anymore. To be honest with the 50 series despite what people said, the bands for me were visible out of the box and never got worse but certainly didn't disappear with age.
To be honest I don't know a recent tv that doesn't have banding or dse. Even lcds or lcds with led backlighting suffer from banding plus they have clouding and backlight bleed too.
The only alternative is going with a samsung plasma to see if they're better.
On the update screen which was my test for the 50 series vertical bands it's uniform to my eyes, although if I focus very hard I think I have some in the middle but I might just be hallucinating
If I'm honest you're just going to have to decide what issues you can tolerate the most and pick your poison.
I've had 30ish tvs come through my house within the last 12 months, about 5 different models with about 5 or 6 replacements and (3 different calibrators come through the door)
They all had issues I could complain about, I'm at a stage now where unless there's something really bad I can't be ****ed to keep boxing up tvs and taking them to the shop looking like an idiot trying to point out flaws to sales people that can't see them in bright lighting.