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I'm in wet & snowy Sweden. I've got shimano XT hubs on my daily commuter. After two years I couldn't take it anymore and opened up the hubs despite repeated checks indicating nothing being wrong with them. There was nothing wrong with them. They looked like new, in fact. I'd gotten new ball bearings and grease already so serviced them anyway. Don't know how rs505 compare but I'm a fan of shimanos.
There isn't room inside a freehub for a cartridge bearing which is as strong as Shimano's 9×¼" loose balls.