My 2014 C4S is coming up to its second birthday shortly.
Has never missed a beat in that time. Only issue was an oil leak from the sump plug after the OPC changed the oil about a year ago.
My comments are as follows, some of them simply standard 911 traits :-
1. Heavy stone peppering of the black sill finisher just forwards of the rear wheel and on the lower bumper immediately behind the rear wheel.
2. Chipping on the bumper and bonnet in line with previous experience.
3. Despite regularly nourishing the seat leather, the driver's seat is already showing creasing in a few places.
4. Oil consumption over 12K miles has been remarkably low at 0.5 litres.
5. Frustrated that after such a long time, that only the Pirellis are N-rated, much to Porsche's shame - dislike the performance on the limit where they just let go with no warning.
6. Got front and rear parking sensors, but not the rear view camera which wasn't available at the time. Worth having the camera if you can get it.
7. Make sure the large cover over the battery in the frunk is in one piece. Very easy to break the locating tabs off.
8. Both tail lights and headlights occasionally show some degree of misting. Have seen some cars with much more severe condensation which should be really changed out under warranty.
9. Protective shark fins at rear wheel arches are now severely marked and going yellow. Will need changed soon.
10. Electronic handbrake takes a bit of getting used to and electric PAS does not really detract from the overall front end feel.
In my opinion, "must haves" for a 991 C4S, are PSE and sports chrono. Get the 3.8 if you can. Good luck in your search.