Someone once told me that it was a good idea to replace your brake fluid regularly, because of its hygroscopic nature and that the water build up will corode the brake system.
When I replaced the wheel cylinders on and old Beetle, the recon ones I fitted were resleeved with stainless steel, which should not have this problem. Is this necessary with the E36 BMWs, brake and clutch, and how often do I need to have it done.