> If all models are identical and have been purchased at the same time, one would expect that the same firmware will allocate the same writes to the same cells

> If all models are identical and have been purchased at the same time, one would expect that the same firmware will allocate the same writes to the same cells Not really, you'd expect them to diverge over time as the cells aren't going to be all 100% identical - they'll have different failures, different error rates, and different read patterns will result in different read-disturb errors, all of which will effect even completely deterministic block allocation. Regardless, as I said, you monitor endurance. Drives are unlikely to just silently wear out out of the blue unless you've been completely ignoring their SMART readings, in which case, more fool you.