The GSX L2 customization surely doesn't disappear by itself. If it does, it's surely because you have *changed* something in the airport configuration, so the .BGL in use is a different one compared to the one you used when you customized it.
As explained many times on the forum, and as explained on the GSX manual, Page 36:
If you provide the scenery with different sets of AFCAD files, just provide several .INI files, named YourICAO.INI, YourICAO1.INI, YourICAO2.ini, each one based on a different AFCAD. The AFCAD pathname contained in the .INI file is not mandatory: if no file with that name is found in the full path, any other AFCAD in FSX matching the name
only will be used instead, regardless of where it’s actually installed.
if you have some 3rd party airports that have a set of multiple AFCADs to choose from, you MUST have a separate GSX .INI file for each of them, because an .INI file is loaded only if it matches the .BGL which was in use when you made the customization.
Most of the times, you might get away by simply making a copy of a working .INI file ( any name is fine, as long it starts with the 4 letters of the airport ICAO code and it has an .INI extension ), and edit the afcad_path parameter in the [general] section of the .INI file to match the name of the alternate AFCAD, it might just work without having to redo all the customization again.
However, if the alternate AFCAD changes/removes some parking spots, maybe to allow for static planes, there might be issues, since GSX won't be able to find such parking spots which were present in the original AFCAD but not in the one currently in use, so you'll have to remove the extra from the .INI file.
Couatl rebuilds airport cache during 300 seconds
That's far too much. Exclude the Addon Manager folder and the simulator folder from antivirus scanning, since it shouldn't take more than 20-30 seconds for a full cache rebuild, even with many sceneries.
