Depending what fluid you use..always flush AFTER race events. Before doesnt solve anything, except make more fluid sales for someone...
RBF600 from Motul, good stuff. But it -has- to be consistently flushed..race or not. Its extremely hygroscopic, and needs to be on a steady path from the master cylinder to the bleed nipple. Especially once abused.
You'd be suprised how fast black, burnt fluid can circulate to the master cylinder from your calipers.
The Motul5.1 can sit in your system for long term use..American style. Fill and ferget.
RBF600 isnt required for autox..you wont get that hot.