I think refurbished enterprise drives usually have a lot of extra protection hardware that helps them last a very long time. Seagate advertises a mean time to failure on their exos drives of ~200 years with a moderate level of usage. I feel like it would almost always be a better choice to get more refurbished enterprise drives than fewer new consumer drives.

I personally found an 8tb exos on serverpartdeals for ~$100 which seems to be in very good condition after checking the SMART monitoring. I'm just using it as a backup so there isn't any data on it that isn't also somewhere else, so I didn't bother with redundancy.

I'm not an expert, but this is just from the research I did before buying that backup drive.