Sometimes paranoia is appropriate. The two killers are operating environment and simple stress.Currently WD Ultra Metal Ed. 4TB. I refresh drives every 3-4 years of use. I don't trust any backup storage. I have had enterprise ssd's die.
That's why I have both Windows PC and Mac set to power the internal working storage drives down when not in use and the PC has internal fans for teh drives.
The external dock is optimum because the drives only get use when hauled out to fetch something and are in a relatively benign environment - my study closet away from power lines and other electromagnetic fields as well as controlled temperature.
The two Drobos have proven their worth - each holds 4 3tb drives for about 8tb or so storage. I've had two drives fail and recovery was swift and error free - just pop in a new drive and the Drobo formats and restores the data.
Nut I reiterate that those commercial external drives usually contain 2 drives in a likely problematic configuration. Even if it's not striped how many folks have the cash to pay for data recovery? If it's worth keeping get a RAID array of some type to protect it. You don't have to buy commercial - there's plenty of cheap PC's or motherboard/processor/memory combos to make your own with a Linux distro that's specifically setup to make a NAS RAID box. I bought my Drobos on sale and for the money and small size I decided to go with that instead