Always use the manufacturer's diagnostic tools to check these sort of things are they do vary between makes and the 3rd party tools (eg: HD Tune etc) may not be using the right scale/conversion to read the values.
If the value is just staying the same or not increasing much it's probably not a big issue. If it's increasing a lot I would replace the drive.
Either way always have a regular backup of all data on the drive.
A multi prong strategy is the way..
1: Weekly full disk image of the entire drive (using Acronis True Image, Macrium Relfect etc).
2: Additionally backup any important folders and files to external drive too.
I would suggest you use a rotating pair of at least two external USB disks. Take the just backed up onto USB drive offsite (friends or family) and bring back the previous weeks one.
I would also consider backing up the data from #2 to a online backup provider like Backblaze, Mozy, etc.
Its more of a universal question, ive got multiple computers, some around 100 some around 280 and it is using hd tune i dont have the time to get to picky with them all so im just looking for a ball park answer