Um well you know more than I do then, as I've only been using them for 15
It could be a problem with the Launch Services database.
Triple click the following, copy/paste into Terminal to rebuild it
/System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/Support/lsregister -kill -r -seed -domain local -domain system -domain user
I found that on my system this fixed an issue where Excel spreadsheets would open in Preview when I double clicked on them and that OS X kept loosing the file association with Excel after I had "fixed" it in Finder.
I suspect that some of the more esoteric issues I have on OS X, such as the above, are a result of running Windows 10 on VirtualBox and suspect that the other VMs may produce similar issues.