Checking the SMART with sentinel is pretty "pro"active as your going to get with predicting HDD failure.
Forget about spinrite..
*This will delete all the data*Make an image or clone it- back it up*
To refresh the disk plug in to your test machine start mhdd. Do a ERASE then just normal SCAN to verify that all sectors are healthy.
You can run a few SMART tests at your pleasure but they wont fix anything.
That is about it.
If you want to be really love your data use some sort of raid system. or just backup what you need

If you get any ERRORS then I suggest you replace the drive or use it on low priority.