I'm actually expecting the drives to go on for closer to 1PB. (more hoping than expecting)

I can't see why it shouldn't, the NAND specs are telling minimum endurance, not maximum so with a bit of "luck" we might go very far.

As for error checking, sure we can do some tests, however, the file system (OS) would report errors for writes, as we don't check for reads I could fit a test that selects some random number of files and just read them before finally deleting, that would make some assurance.
I'll have a look at MD5 testing as well.