I was using desktop grade Seagate/Hitachi drives successfully for years on a hardware RAID 6 controller. I used to get a timeout error once every couple of months, it would rebuild pretty quickly and since I'm on RAID 6 it wasn't much of a concern.
Just recently switched to WD SE "enterprise grade" drives and despite having this TLER feature, right after a successful migration, I've had several timeouts from multiple drives.
This whole TLER thing just feels like a bit of a placebo to me, after what I've experienced anyway. So much for "enterprise" grade.