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This could be a possibility. It would explain why I can’t get the caliper perfectly centrally aligned.
Why would a bleed make it feel temporarily better? I don’t have a good understand of hydraulics so interested to know.
samrensho-
Yeah, the constant caliper misalignment is another sign of a sticky piston.
To be honest I have no idea why it rapidly shortens the bleed intervals, but would love to know.
It's pretty easy to rectify; remove pads, advance pistons individually (by holding one piston back at a time with a wide plastic tyre lever or similar and carefully pumping the lever), rinse with brake cleaner to loosen up the dark shadowing stuck to the ceramic and then use a lint-free cloth to gently 'floss' the piston clean. Then syringe some fresh mineral oil onto the pistons to lube them before resetting them, clean everything with brake cleaner, bleed, reinstall pads.
If you wanted to pop down to my workshop in SW14 and I'd be happy to help out.
Harry 
Check if both pistons are moving freely and equally. I've seen lots R7000/R8000 calipers do this when one of the pistons has become sticky or completely stuck.