Master cylinder/caliper seal replacement – every 2 years
This is one time when we don't recommend religious following of the Service Schedule. Dust and fluid seals will last a long time, even in severe-duty conditions.
The manual states “Caliper Piston Seal and Dust Seal - replace 2 years “
You need to examine the caliper dust seals when you change your pads. If one is damaged, replace them all. The linked article will also show you how to check the piston fluid seals. The dust seals will fail before the fluid seals; that is their job. Check your brakes often, and if there is any sign of fluid leakage, service your brakes immediately.
The manual states: “Master Cylinder Cup and Dust Seal - replace 2 years”
Brake master cylinders, even when old and terribly neglected, will seldom give any trouble. The manual is basically saying to check the plunger part of the cylinder, and that's what you should do: check it. If there is any sign of leakage, then you'll have to take it apart and find the problem.
Be attentive to your brakes, but it isn't necessary to replace the seals as often as the manual suggests. Calipers always need work before master cylinders, which is kind of too bad, since master cylinders are much easier to work on.