How often should 5.1 brake fluid be replaced. I've had made in for just over a year now and I'm sure the brake pedal is not as firm when braking hard as used to be. Should the fluid need changing after this length of time.

I used to do it every year ... at the same time as my annual oil change, etc. (I only ever did about 5,000 miles per year, at most.)

When was your last oil and fluid change Dave?

DOT 5.1 should be good for two years in situ before requiring replacement, albeit a flush every year does your system no harm.

If you've got problems then there's perhaps a leak or another mechanical issue affecting what's going on.

Changed fluid and flushing system every 2 years....

I really must do mine... Had a moment today where the brakes just did not work straight away!!! Will try a flush and re-fill first..

Every year I would say and recommend the Motul Brake Fluid, as it will withstand very high temp and not break down so quickly.

good stuff

http://www.opieoils.co.uk/p-894-motul-rbf-600-factory-line-racing-brake-fluid.aspx

Dan, sorry ... only just noticed this post of yours!
The last fluid change (all fluids) will have been at the last service at Motormech ... as indicated in the service book. It had a service every year at the same time ... so sometime in March '10, I'd guess?