My SLX rear brake is a couple of years old now, seen various alps trips and uplift days, it’s starting to cook real quick on those big descents, even if I give them a really thorough bleed, this didn’t use to happen to them.

Are they just getting old and tired and past their prime (ie pistons/seals/bores getting out of shape) or am I simply not giving a good enough bleed?

What are peoples experiences?