Write-mostly workloads to a bunch of consumer grade disks will have errors that you may never detect.
At Backblaze, we try to pass over the data about once every two weeks. We re-read it from disk, recalculate a SHA1 checksum to make sure there wasn't any bits flipped or lost. It is my (informed) opinion that *ALL* hard drives and *ALL* configurations will have errors you may never detect unless you do this. You can't ever trust any file system.
I think many people assume RAID does this checksumming, as far as I know RAID handles entire drives failing, but it doesn't really have anything to do with a drive that has begun to fail and is starting to flip a few bits here and there but the drive is still mostly responsive.
After all this research, Backblaze still pick the highest failing drive.
Disclaimer: I work at Backblaze. Every month we ask a list of about 20 suppliers for their best price on a variety of drives. There is a little spreadsheet we have that kicks out which drive to purchase based on those prices and drive failure rates. Even if Hitachi is the very highest reliability in our application, it only justifies a SMALL price premium because when one drive dies, we don't lose any customer data. It saves our datacenter IT team 15 minutes to *NOT* swap a drive, so that's worth 15 minutes of salary to us, but not more.
What the gods would destroy they first submit to an IEEE standards committee.