Picture this, you ride the same stretch of rock garden every 2 weeks 9 months a year. You don't get scored for riding it faster or slower than anyone else, you just have to get from point A to B in no less than 4 minutes and maybe, what, no more than 4 mins 15 secs. The rocks don't move between rides. The weather is always the same so the traction and bumps and mountains are always the same. You can memorize your everyone move. Wouldn't you train so that you can handle the physical and mental output? Sure, your style points may fluctuate, that's human nature, but wouldn't you be able to get from point A to point B without total exhaustion?