It's a good idea to change the oil in these units at least biannually and to use the recommended quality products. Brake and clutch hydraulic fluids are also subject to heat and water absorption. As a matter of fact, to avoid the possibility of a drop of accumulated condensation ever freezing and blocking a brake line, brake fluid was designed to disperse that water throughout the system. The problem is that the water disperses all the way to the brake piston seals which have oxygen from the atmosphere just on the other side. When old stale brake fluid is allowed to sit long enough, as in a Maserati which is only driven occasionally, a ring of rust develops just behind the brake piston seal.
Brakes also get hot.
The more you need them the hotter they get. Water turns to steam if it gets hot enough. Hydraulic fluid is incompressible, steam is not. The possibility exists that you might be coming down a long hill and have to use the brakes a lot. The pedal could go to the floor as the steam in the brake lines compresses under pressure.