Have RS 21 months.

After 11months had 5k miles up. Got 10k service done, which is basically an oil change. Almost 1 year later (last week) had 11k up, and got the 2year/20k service done. However garage said wait a while to change brake fluid (despite book saying to change it after 2 yrs) as it is a 3 hour job that requires the computer to monitor all the fluid been taken out of the system, and it also involves some vacuuming. Costs about 150 euros. So instead they just cleaned the brake fluid bottle and filled it. Question is - how soon should I actually get the stuff changed ?

Hi........if you can get the fluid "boiled" there is a proper device (which i have) to do this, dot 4 should not boil below 180c if it does (i.e it means it has water ingress) it should be replaced. Brake fluid is hygroscopic so it absorbs moisture from the air. The only real way to change it is with a pressure bleeder...refilling the reservoir with clean fluid as you say the dealer did is cheating not only you but the future condition of the braking system..:thumbdwn:

Phil

Every 2 years a stated.

Can be done with a bleed bottle if you really need to, pressure bleeding is better though.