Yes, it has to do with the chemistry at the electrodes, as well as the issue BigDave mentioned. I think it's been covered in the China Shop by Chem_Geek, but I don't have time to go poking around for it right now.
But, your cells will last longer that the higher level, since cell life is proportional to ON-time, and they'll be on less at the higher CYA, even with the higher required chlorine levels. Read through the Best Guess page, linked in my sig, for more info.
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