i've heard of many claims here that their pleather lasted for decades and are still going well, well i don't really know about that, i know their longevity depends on the environment but i also believe they will eventually fail. i've done many different types of care from nothing, to leather shine, rubber protection, bee wax to mink oil, while i believe the rubber protection and bee wax/mink oil does help prolong it's durability (rubber protector adds a coat on it but makes it look thick), they will still deteriorate from the inner side. So what ever sealant you apply on the outer side will not protect deterioration from the inner side which is more important because the pleather is somehow glued onto the fabric base and humid et al will attack from the inner side too and the pleather layer starts losing it's adhesiveness and starts flaking. a layer of top coat helps keeping the pleather layer together in 1 piece but it will not prevent the layer from coming off the fabric base.
i guess they couldn't use durable pleather like those on motorcycle seats because they would be too thick. also different materials within the costume (pleather mixed with rubber or even plastic will start to eat each other up due to chemical reactions).
