The latest theory is that during fast charging, the pressure inside the cell builds up and the cell actually slightly vents during each charging cycle. The reduction in performance is actually caused by a loss of electrolyte.
Have you heard anything like that?
No ,I thought they only vented at something over 250 PSI and the China made cells have reportably a one shot vent. This may be BS but that is what I heard anyway.
I do believe that fast charging / heat drys the paste next to the plate and can cause a decrease in life but then I never claimed to be an expert.I have however sawed a few old cells in half length to see what the insides looked like.