[roadracer311]

I do it at 1 year or 5k miles whichever comes first. There are definitely some things, like oil and brake fuid, that need to be changed on a calendar basis. The owner's manual is pretty good about letting you know which ones those are.

Spark plugs are another one. Porsche says you can run them for 60k miles, but also recommends changing them out after 4 years. That meant I did mine at 20k miles.