I guess I should mention QuickPAR here. For critical static data that isn't changing, one option to ensure long-term accuracy of the data is to run QuickPAR over the folder and create a few repair blocks. That way if you ever find an odd hash error you can easily repair the files. The catch with this is the last version released doesn't support subfolders, so you can only PAR2 files in a single folder, not an entire folder tree.

I've been involved with QuickPAR for a long while and was part-way through writing an alternative, hopefully improved version with support for subfolders when development time dried up. I'm hoping to restart that work. Maybe some of my code could be retargetted at a more automatic test-and-repair regime than a simple manual PAR2 test...