I also generally tend to keep drives powered up, and they indeed tend to live long. Still, I have to be on alert for failing drives. I had four of the WD30EFRX together in a 2x2 pool (roughly equivalent to RAID10). One day, one of them began showing checksum errors after a scrub, and I replaced it with a Toshiba DT01ACA300.
Once the bad drive was out of the pool, I ran a full self-test on it, which it failed. I did at least get five years of service out of it, but in any case, it's time for me to think about some newer hardware.
For my next NAS, I'm kind of leaning towards using 2x8TB mirrored, with a third drive to be rotated into the mirror, splitting off the rotated-out drive as an offline backup.
Once the bad drive was out of the pool, I ran a full self-test on it, which it failed. I did at least get five years of service out of it, but in any case, it's time for me to think about some newer hardware.
For my next NAS, I'm kind of leaning towards using 2x8TB mirrored, with a third drive to be rotated into the mirror, splitting off the rotated-out drive as an offline backup.