This one is simple. Change the damn brake fluid. You should change it annually, but I'm sure you don't. I change my brake fluid before every event. That means I change it five or six times a year. People kid me about my spotlessly clean brake fluid, but I've never lost my brakes in 10 years of running track events. I see other people bleeding their brakes at the track and changing pads in the middle of the day. That's just plain stupid. I don't go to the track to work on cars. I go there to drive. Get the work done before you drive through the gate, not in the middle of the afternoon when your friends are driving around the track.
I'm not going to recommend a brand of brake fluid. Most of it is pretty good. I used Ford fluid for years. It was cheap and available at the local Ford dealership. I've also used Castrol fluid, but not the expensive stuff. Lately I've been using the Wilwood 600 Plus, but the 570 would be just as good for most of your needs.
Brake fluids absorb an average of 2 percent or more of water in the first year of usage. In that period, the boiling point can drop from 401 degrees F to 250 degrees F, a reduction of over 150 degrees. It's not uncommon to have caliper temperatures exceed 200 degrees. At 212 degrees, this collected moisture will boil, causing vapor lock and brake-system failure. I'm not real big on the DOT 5 silicone fluids since they're not hygroscopic. That means as the moisture enters the system, it's not absorbed by the fluid, and results in beads of moisture moving through the brake line, collecting in the calipers. Additionally, DOT 5 fluid is highly compressible due to aeration and foaming under normal braking conditions, providing a spongy brake feel. DOT 5 fluid is best suited for show-car applications where it's anticorrosion and paint-friendly characteristics are important.
Racing brake fluid is intended for use in racing-type brake systems that undergo frequent fluid changes, so exceeding federal standards for wet boiling points is of little concern. Racers don't care about the wet boiling point, since they change fluid so often it never contains any moisture. Racing brake fluids always exceed the DOT specifications for dry boiling points. The dry boiling point is more important than the wet boiling point when used in a racing brake system. Just the opposite is true for street cars, where the fluid is seldom changed. If you flush your brake fluid before each event, it won't have time to attract any moisture either.