How about backing the non-volatile w/ volatile? Not 1:1 necessarily, but 1:2 or 1:3, plus a capacitor and electronics to get the cache onto the non-vol when the power drops. This would effectively negate the max writes problem...and they've probably already implemented like that. Or just shoving data forward in a loop per cell to ensure cells share writes equally, which is probably closer to what they are doing. Great, now I'll have to go read up on them.