If they are kept in a wardrobe or on a clothes rail, the DWR can rub off I'm told, or in transit folded up and stuff. Which is why they might need re-proofing or at least tumble drying as soon as you buy it.
The fabric itself doesn't degrade though.
Seems a bit odd though - a jacket should last many many years, and you should be able to get a decent bargain at some point as your current one gets older. There will be better jackets and fabrics around for the same price by the time any jacket you buy now is worn out.