The problem was not a fault of design - the problem was mechanics using petroleum grease on the slide pins with swells the rubber parts and also allows water to mix with grease. You are supposed to use a silicone grease on them - and this car being General Motors they even have a better version, silicone grease with teflon added to it. Silicone grease wont be washed away from water and if you check it years later it will still be wet n fresh.
By rule of thumb, brake fluid flush is mandatory every 12 months with any off the counter brake fluid conforming to US DOT3 Standard. If you dont then the system will rust internally