Before first fill is all that is needed.
Propane cylinders are typically shipped with air
That air needs to be purged.....air mixed with propane will cause popping noises/regulator issues etc.
Purging can be done using:
Propane Vapor (purge kit with supply cylinder and purge valve) Vapor is transferred 4-5 times in and bled off to remove air. Then cylinder can be filled with liquid propane
Vacuum Method where a vacuum is pulled on cylinder and then propane vapor is transferred in and then liquid propane can be pumped in.
Should NOT need purging again UNLESS
Service valve is replaced.....air in cylinder