Sorry to say this but you don't understand how brake pistons work. They do not move in and out of the seals every time you apply the brake; apart from anything else, what is there to push them away from the disc?
What happens is that the pistons get pushed to the disc and stop and then when you de-compress the fluid, the flexibility of the rubber seals causes the pistons to settle back a short distance away from the disc. Every time you squeeze the lever the rubber seals are deformed and the brake is applied. As the pads wear the pistons do creep through the seals but the process is very slow.
If you've ever removed a piston from a brake caliper you'll know how damn tight the seals are and you'll realise that they can't slide in and out through the seals.