I own an 04 Turbo Cab with 11,500 miles.

1) Change the brake fluid every two years
2) No need for timing belt but make sure you do check a couple times a year to make sure no cracks. I would say change every 5-10 years based on how the car is stored and in what type of climate
3) Oil change every year or every interval (mine is every year... less than 3k per year)
4) spark plugs... no. Maybe after quite sometime but mine have not been changed and the car runs like it came off the line yesterday. I would base replacement on emissions, gas mileage, how smooth it runs, etc. Only change early if you can't stop thinking about it or it has been a very long time... 10-15 years.
5) rubber deteriorates at different rates based on climate and storage. I live in a fairly dry and warm climate so my rubber should not wear as fast (that came out weird) as someone in Michigan for example where they have 4 seasons, humidity, snow, salt, etc.
6) power steering fluid: I changed mine when I replaced the clutch accumulator and slave cylinder. I took out as much as I could since I knew it hadn't been done since new. probably not a bad idea
7) coolant: I changed mine this year since it had never been done and I couldn't stop thinking about it. Call me crazy but time can be bad and even though Porsche says it isn't needed I bet these are based on driving the car rather than owning a garage queen.

That is all I can think of now... I am sure there is more.

Hope this helps,
Bryan

 

Thanks for all the advice!