Depends on if it's your first time or not.

I find that the night before a big event (of almost any kind) I perform better the less sleep I get. I got 3 hours before my first IM, and it wasn't a factor.

If it's not an "A" race or a new race I can sleep well. If it's a new race or a longer distance. I get wound up and don't sleep too well. As long as I get enough sleep 2 nights before it's no problem.

Richard

To add to what Richard posted, I've Long heard that the crital nights of sleep are the two nights prior to night before race. Fo same reasons.. If it's an "A" race nerves will kill any good sleep. Along with possibly the need to travel to race site etc...

Two years ago as a TNT marathon coach I went with a bunch of runners to FL for Disney marathon. I wasn't racing and an old college buddy lives in orlando, so we linked up for a few brew-ha-ha-s I made it have to the room at about 1230... My roommate who was doing his first marathon was still up flippin channels and says - dude I CAN'T SLEEP!!!!! We had to be up an out of room by 02:00 because of the rediculus time line Disney follows for the race. So basically, he didn't get any sleep night before race... Didn't bother him, but he crashed hard the next night; half a beer at the victory party and he was practically drooling oin himself..