On my prior VW I did brake fluid changes every 2 years, and I swear, I could feel a difference afterwards. Maybe it was in my head, dunno. But I sure felt better... My '99 never had a fluid change, and when I changed it in 2016 nothing but green fluid came out. I thought I had a decent flush but I wasn't going to spend hours pulling quarts through... Decided to change again this weekend and nope, still getting lots of green fluid out of it. Something going on in there. Am trying to aim for once a year now. I'm thinking, if I just empty the master cylinder and then pull an ounce or two per wheel, once a year, then the fluid never gets all that old, and I don't have to worry about doing a full flush every time. The fluid itself can go 10 plus years, so a little every year is overkill. Yet cheap.