I think if you are careful with fitting them and don't go too mad on the sizing they will last for several years. The Feinwerkbau Sport ones will definitely turn into cheese after 10 years. So, no, they are definitely not as durable or forgiving as leather but they are far more efficient and they are not much money to replace when the time comes. A leather seal can be forced past razor-sharp edges, endure heavy dieselling, seal an out-of-round cylinder and last for decades on no lube (provided the seal has been well lubed at the beginning of its life) and can be replaced with a substitute cut from an old belt, so they have advantages. If they go hard and dry they can also be refurbished with a roughing up with a file and a soak in oil overnight. The smell of a leather-washered springer that is 'on song' and combusting oil at the right rate is delicious!Originally Posted by 45flint
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