i dont beleive there is a set time or milage for replacing clutch fluid. the brake fluid should be changed out @ 90k. so i would say just do it when you flush the brakes. clutch fluid isnt really exposed to severe heat or pressures, so it doesnt break down like brake fluid in the brake system. i think you would be fine just to leave in there, and when the time comes (if it does) to replace your clutch slave cylinder, then just do it then. hope that helps