Mine had never been changed and was beginning to split when I bought the car. So a new one ordered from Porsche and only about 30 minutes to remove the old one, bin it and replace with a brand new part.
Clear view of the 'corrugated' plastic curtain
The spoiler is a lovely part of the car....photographs well...
The other part worth mentioning is the spoiler motor bearing. The corrosion and failure of this part is fairly common and is obvious when listening to the spoiler when it's going up or down. If the motor is making a grinding noise, almost certainly the bearing is gone and needs to be replaced.
The bearing is very inexpensive, and the job is both straight forward and satisfying.
It involves splitting the drive assembly, removing the old bearing and replacing with new. Re-pack with grease, re-assemble and refit in situ.
Spoiler is virtually silent now.