Brake fluid has to be changed after some interval, longer or shorter, all fluids in the car do.
All German manufacturers require the brake fluid change to be done each 2 years, even in the old VW Bugs(drum brakes all around) the recommendation was the same. In my 1966 Bug(now in repairs
) I've not changed it for 2 and a half years, not even completed in the meantime, and when I've looked at the reservoir, the liquid inside was black. Not "a bit rusty", like others say, but
black like sewage. Obviously I've drained immediately the brakes and refilled...
Conclusion: you may change the fluid in the Pontiac or Mercedes, or you may leave it as it is. It's your risk
~Nautilus