If you buy a hard drive today, there’s a 90% chance that it will survive for three years. If your drive makes it to the three-year point, you would be wise to back up your data, as there’s a 12% chance per year that your drive will die.
It’s also worth mentioning that Backblaze’s drives are spinning constantly — these failure rates are for drives that are turned on 24/7. Your home computer probably isn’t powered up 24/7, and thus the drives may last longer.
Store your data in three locations. My computer is backed up via Time Machine to a networked attached storage (NAS), which is further backed up by an external hard drive. I’m not keen on cloud backup software because internet connections are so slow for the amount of data being backed up, so I keep my copies local.
It doesn’t hurt to keep a bootable copy of your drive around for some of those hard failures. Use Carbon Copy Cloner for Macs.