I think the only advantage of a TPL file is that you must 'Save As' for every new job.
However, you must 'Save As' if ever you want to update that TPL file - and make sure you are saving as the correct file.
The company I work for has 1000+ standard plans and they are all just saved as PLN files.
The thing is though, we also give our users read and write permissions to access these files (at a network system admin level - not thorough Archicad or BIM Server).
So unless the users has standard plan access, they can only read the files and must 'Save As' to a job folder to continue working.
The easy way for them to start a job is to simply copy the standard plan and paste it in a job folder.
Rename the file and start working on it with a simple 'Save'.
With good network administration and backup routines you should be OK with just PLN files.
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