Just wondering if it would prolong the life of the origional interior to use seatcovers or not.
I only have the drivers side covered as I rarely take passangers but, as the car is ungaraged and out in the elements of sunny Melbourne, would the seat material deterioate quicker if left uncovered?
- Adam

Yes, it will deterioate quicker in the sun. The sun really isn't good for any upholstery fabric or vinyl. The seams will probably start to split also because the thread they would have used may not have had any sort of UV treatment. Go the seat covers. if your windows are tinted it might be ok though.