How often must I update to get GSX (and also Zurich and Basel airport) to be actually up to date?
Only when the release notes say there are updates.
I ran both updaters at least 10 times today, and both still want to update my FSDT products.
the updater doesn't "want" to update your FSDT products. When you run it, it CHECKS for updates all your FSDT products, and will only downloads updates if needed. Some files are always supposed to be downloaded each time, which is normal, as explained in the Sticky thread with the latest release notes.
