HOW does moisture get to a Brake system?????? Just removing the reservoir to check fluid level is NOT going to introduce moisture(humidity) to contaminate the system. The OEM recommendations (IMO) are CYA for them. A Motorhome would be a 10 year flush and replacement. Automobile--Never. How many people out there have had an actual first hand knowledge of a Brake Failure problem/accident that was determined to be a failure to flush their Brake fluid? In 50 years of driving and 40 years in the RV service, I have never heard of such a problem on Motorhomes or Auto's. Doug