My airline measures the acidity of the hydraulic fluid. The fluid changes Ph due to it being heated by braking . We operated a widebody Airbus for over twenty years predominately using full reverse and manual braking. In the latter years this was changed to idle reverse and manual braking to save fuel. It soon became very noticeable that the brake packs were being replaced more frequently and also the acidity of the hydraulic fluid was becoming noticably more acidic which then led to more hydraulic leaks as the seals were degrading.