Many urban myths surrounding car tyres. Not sure why some people think the product is any different to other consumer products. You get what you pay for! Buy a good quality, probably imported, tyre and it will last a lot longer than 4 years.
This "don't buy old stock" needs qualifying. It is proven that heat and exposure to the sun(UV light) is the biggest killer of car tyres. So it follows that it has to depend on where and how the "new" tyre is stored. If the dealer puts it outside on display in the sun, then expect it to start deteriorating, and don't buy it. If it is kept in the wrapping it came in from the factory, out of the sun in a cool store room how is it going to deteriorate? Yes, some evaporation of base chemicals can occur in storage, but it is a very slow and limited process when stored correctly. Ideally, any rubber product should be stored in an air conditioned room, more so in a hot climate, but that is unlikely to happen here.
A lot more reduction in tyre life is caused by bad maintenance, mostly incorrect running pressures, followed by wheel alignment and worn suspension. Parked out in the sun, being used or not, is also about the worst thing that can happen to a car tyre.
I have a set of "Nitto" LT 245/75 R16 tyres on my Land Rover. They were fitted on 09/05/2012 and have now done
42K Kms and look and ride as good as the day they were fitted. BUT, the car is rarely parked out in the sun, and the pressures are kept correct using the 4 psi rule that I have mentioned previously. I do not rotate their positions, and in that time have only had 2 of them repaired because of a nail. The steering and suspension is kept in good order.
