I still have Hd's 10 yrs old that work ok..

failures :
many times a drive will start "clunking" or other strange noises.. time to back up the data..
other times, no noises will occur but you start getting more and more bad clusters when doing a scan.
that's when I grab my copy of "spinrite" from grc.com and let it do it's magic..
I've fixed a number of drives with this tool..
can't say how long it will go before I need to run it again.. haven't had to yet..