First off what a tight job! Took me and my son 3 hrs .So I pulled up renntech diy for changing the belt on a 2006 turbo. Everything was going good on dismantling and only took off what I needed up top. We'll I thought I could get away without removing the left air box and maf sensor wrong! So I get the belt off and realize that the crankcase vent line needs to be disconnected to get belt out. So I try and undo the connectors and bad luck strikes. Porsche in all it's wisdom used ribbed plastic lines for the crankcase vent and sure as **** the heat over time has made it brittle and snap breaks . So I continue and got the old belt out slip new one in and with my sons help route the new around he pulleys in about 15 min. Started reassembly and for repair of the crankcase vent line I picked up some 7/8 Id rubber hose slipped over the broken ends with clamps and resecured it in place. Reassembled everything start it up and good to go.

So in reality if I was to do again I'm sure I could knock An hour or more off just from not having to puts around with repairing crankcase vent.
You only need to remove the left air box and top portions
Do have patience as it will test you
Sit back and take consolation that you probably saved your self a few hundred buck problem spent better on beer or fuel so you can stomp on them turbos.
But I do have a questions when I tried the tensioner pulley before putting new belt on I noticed there was some play in it and the shock absorber is this normal or could it be the cause of my humming / whining sound on idle and driving that is present through out the rpm range?

 

I've heard it mentioned to change the belt tensioner every second belt change.
Apparently they do wear.

 

We'll this is my first. What's the expected mileage of a new drive belt on the 4.5 turbo? How long mileage wise should I plan to go before changing again?

 

I just did my belt also, exact same scenario. Broke that crappy vent tube also, talk about pissing me off. I was able to wrap mine in tape and zip tie it.

 

There isn't a specific mileage to change the belt.

It's an on condition evaluation which is carried out at each service interval.

Changing every 70k miles is common.