You want it open as soon as possible, so as said above, as you approach the finish line, push the lever then go about your business. It will all feel natural and automatic. The safety is enormous. No matter what happens, brake failure, fire, throttle hung, car gets out of shape, blowout, no matter what, you are in so much better position. You'll like it so much won't be able to go back. It just feels unsafe...because it is.