I'm not sure what you mean by 'safest,' but I prefer to have it in my shared Sage directory, alongside the folder that holds the current version of Sage 100, and Sage Business Intelligence templates, etc.  That way, I can have IT backup that whole share nightly.  That said, if you need to have security on the folder due to sensitive data, you may want to have it outside of the area that is shared, since that is probably set to full control for all accounting users, at least.

I wouldn't want to put the folders anywhere that would be written over or messed up with updates/upgrades. 

We have our entire drive on backup.