From the datasheet for a Spansion 512MB NAND flash chip:
Program/Erase Cycles
– 100,000 Program/Erase Cycles per Block Typical
– 10,000 Program/Erase Cycles per Block Minimum
So you may start to lose some capacity after 10,000 cycles but it shouldn't start to drop significantly until around 100,000.
They sell two versions of the part, a 100% good version and a version with known defects which does requires ECC.
I'd guess that the usable cycles for a known good part if you used ECC would be a lot higher however since the versions with defects are going to be cheaper I'd guess that that is what will be used in drives.
And as you say, under any realistic use model 10,000 cycles translates to a perfectly acceptable life anyway.
datasheet (pdf) for those who care.
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