The definition of wear out is more than just the SSD declaring the cell bad, or the SSD failing suddenly. A cell is technically declared worn out when the chance that the cell suffer charge leakage after N months at temperature T exceeds probability P. (Where exactly what these parameters are are a secret that the SSD vendors don't disclose. There are some standards, but the SSD vendors don't necessarily use those standards when the make promises about their product's wear endurance.
So even though an SSD might last for 1.5 PB's worth of writes, there is no guarantee that if you were to then put the SSD on a shelf and wait nine months, that they data will still be good. This is probably one some vendors will declare themselves to be dead after so many gigabytes worth of writes, even if the flash cells haven't "failed" yet. Otherwise users might depend on the SSD's contents being retained, when in fact they might suffer data loss.
But of course, this doesn't really matter much, because you treat all data stored on SSD's as a cache, and do regular backups, RIGHT? :-)
So even though an SSD might last for 1.5 PB's worth of writes, there is no guarantee that if you were to then put the SSD on a shelf and wait nine months, that they data will still be good. This is probably one some vendors will declare themselves to be dead after so many gigabytes worth of writes, even if the flash cells haven't "failed" yet. Otherwise users might depend on the SSD's contents being retained, when in fact they might suffer data loss.
But of course, this doesn't really matter much, because you treat all data stored on SSD's as a cache, and do regular backups, RIGHT? :-)