Gentlemen, if I may.......
We get our brake fluid from ATE and all the cans say ..Change Yearly.
BMW Service Indicators have a yearly check that self times and brake fluid flush is an Annual check.....Coolant biannually.
Next caliper you build check the muddy crap on the piston....solvent wont wash it offf...its mud...thats settled in the most forward meander.
Change brake fluid every year...its cheaper than caliper kits, w/cyls and brake material....and safer.