COLB's summary is excellent.
One variable that is clear from others is whether or not the car is to be used and enjoyed on a regular basis, or tucked away in a garage with the hopes of price appreciation. If the latter, then the car is falling in to a 'collector' class and the miles are critical. Otherwise, the moral of the story is to get a solid example (good maintenance, not damaged) and have fun. After all the Porsche owner's manual doesn't describe how to maintain a car that is driven out of the garage onto the driveway for washing, dried, and re-parked.
I suppose the downside to the higher mileage/ gray beards is that once you have one, its not an 'investment'...though that's a delusional term for many owners. So as the 3rd owner of a clean 212K mile original engine garage-kept car that's never left SoCal
this thread has been very helpful.
thanks to all, and perhaps some one can start a mileage poll to see how the grey beards are holding up.