I've read in a BITOG post you should never push back the brake fluid into the ABS when pushing the pistons back into the caliper when changing disc brake pads. Instead it is advised to open the bleeders and let the returning brake fluid leak out. Is this a valid idea? I have never opened the bleeders when I changed brake pads; I just push the pistons back and let the fluid reenter the master cylinder. And I never had anything bad happen thereafter.