External failure rates are hit and miss because frankly, they often get abused.

I’ve had some last for 10 years, other for 2, and I’m not kind to mine.

I’d say they have 2 issues to deal with: temp and being dropped. The cases have no cooling, and larger drives need greater cooling than smaller drives.

I currently have 2 external drives (4 TB each) I use for local redundancy. When sync happens, they get quite warm, so I keep an old 80mm case fan on them. These are 5 year old drives that have been running this way for 3 years. SMART doesn’t report any errors or high temps, but without the fan I’m sure it would.