For high performance applications, it is recommended that the hydraulic fluid be flushed on a regular bases to remove any moisture that is in the system. Moisture in the system will hurt the performance of the hydraulics, and cause premature failure to the lines, rings and seals. I have spoken to some people that will not store the fluid, they will only use fresh fluid from a sealed METAL bottle, because of the possibility of water contamination. For my money, I change out some of the fluid each time I open the system. In theory, if you never open the reservoir, then there is no way for the moisture to get in to the system.. I usually don't keep a bottle of fluid around for more than a few months. Dan Wrote: > Is this true even if you bleed the brake and clutch system every two years or so? I was told that > they should be bled every few years to extend the life of the seals.