Write process details are critical to holding off wearout, my
small experience with flash (really EEPROM) cell characterization
says that write time and voltage are very strong reliability
(retention / wearout) accelerators. You would probably want
to be real sure that, for example, the write supply voltage
is reliably within spec (or even skewed to the more reliable
end of spec) and similarly write cycle timing (although these
also interplay, to retention time via the written charge total).
Going too low will give you a soft retention failure while too
high will give you permanent degradation.