> I was using just regular desktop grade disks so that happened every 18 months or so.

That seems unusually bad. Up until earlier this month my old raid array has been mostly desktop drives(just upgraded it to IronWolf NAS drives though). I did finally do the upgrade to new drives because one died, but that drive was manufactured in 2011, and the rest of the drives are from 2010, 2013, and 2015. To be fair I've not gone five years with out a failure, I think the 2015 drive was added about 3 years ago(being my actual desktop drive before that), but otherwise have had good luck. In fact, I think my most recent failure may have been accelerated by my server being put into a temporary case with poor air flow.