I have 3 which are fine and sold a van recently with another that was fine, as mentioned above these are out of cars around 40 years old and like anything if they have been abused they are going suffer, its probably does come down to the materials, design etc of them but I dont think they were ever meant to last forever. The choice is out there to either have them reconditioned or buy a reproduction, I do know a guy who has a brand new (NOS) genuine never been fitted to a car but reckons he want $2000 to part with it or a $1000 for another one which is on his car which still has all its grain, you could buy a fair few repros for that money.