Coolant and brake fluid are routine maintenance items every two years in most areas, though the "extended life" coolant type specified by MBZ can sometimes go three or four years. I've worked in the car business off and on much of my life, and I can't tell you how often people get into very expensive repairs due to corrosion in their braking systems from not changing the fluid as needed. Audi's recommendation is consistent with most other manufacturers.

I do have a question, though. Has anyone changed over to a DOT5 (silicone) brake fluid from the specified DOT4? It's non hydrophilic and therefore doesn't require routine replacement, but in some applications tends to weep a bit from seals. Anyone have any experience with this?