You surely don't have to do a cache regeneration every time.
The cache regeneration is automatic and is starts automatically when you install or uninstall new scenery. However, as explained in other threads about renaming AFCADs, you MUST "Restart and rebuild the airport cache" after a rename, because renaming a file won't update the folder last notification date, which GSX use to know a scenery has change, so it won't have to check each file, one by one (there might be many thousands), because it would slow down the startup a lot if it did.
A rename might happen if you use 3rd party sceneries that have utilities that switches between several configurations.
But no, normally, you don't have to rebuild the airport cache.
