Let me correct myself.
If you go all winter without washing the underside then you may have to worry about rust. But I have never seen a Boxster with rust, and speaking from experience you don't have to worry about rust if you you wash the underside of your car every few weeks in the winter.
There is no need to baby these cars, they where made to be driven. And the ones that are often have far fewer problems, in my experience
(Sorry, if my previous post came of as rude.)