How Long is too long to Race

Coming up this Sunday is the Coca Cola 600 at Lowe's motor speedway, what will happen in this event, will we see an unlikely winner like last years Jamie McMurray or will one of the most consistant Lowe's drivers, convienently Jimmy Johnson who's sponsor is Lowe's return to victory Lane? The big question why do we need to see a 600 mile race. I'm a huge Nascar fan but to sit and watch 5-6 hours of racing is a bit much. Wouldn't it be something in face of the energy crisis we are all in if in good faith they shortened every Nascar race by 100 miles. How much gas would this save, 43 super stock cars. This would shorten the races considerably and no doubt increase attendance both at the track and at home on the TV as people are time starved and sometimes can't handle that much.