Most Wilderness Classic racers use caffeine in one form or another during the race. Even though it's widely used, you can still get an advantage with caffeine with a little planning. The results of studies vary on whether short term athletic performance is enhanced by caffeine but most of them point to caffeine helping the body burn fat during endurance events. Burning fat is key in the classic and other ultra-endurance races. It's also very useful for staying awake and can enhance moral as well.
A few weeks before the race, taper off your daily dose of caffeine and don't use it again until the race. The effects will last longer and be stronger if you haven't been using it every day. Wait until you think there's no chance you can walk another step in the race before you take your first dose. This is where caffeine will give you the greatest advantage. You'll be so hopped up on adrenaline the first twelve hours of the race, caffeine won't give you much more help.
When everyone else is laying down on the ground for a doze and you're still staggering along making distance, you can several miles on your competitors. An average pace of two miles an hour is decent in the Wilderness Classic so if you can keep going for an extra hour, that's two miles farther ahead you'll be.
Another important point to note is that caffeine is not the same in every form. That latte you buy every morning from the local drive-through stand is chock full of high-octane garbage caffeine that will give you a headache and just make you feel tired in a couple hours. It's also full of pesticides and fertilizers which won't do your body any favors. Caffeine pills are also made of cheap grade caffeine. They'll give you a good initial boost but the aftermath isn't pretty.
Buy some quality organic coffee and you'll feel much better and when it comes time to cut back or even stop drinking coffee altogether, the withdrawal symptoms will be much less painful. Kaladi Brothers in Anchorage has some great organic coffee that tastes great also. While I'm on the topic of healthy caffeine, typical drip coffee makers not only ruin the taste of good coffee but they also dump plastic into your coffee pot from the hot water and acidic coffee coming in contact with the plastic coffee maker. Use a stainless steel percolator or better yet, a fully stainless steel french press. You'll be amazed at the difference in taste and you'll avoid the pthalates and other estrogen mimicing chemical compounds that come from plastic that you really don't want to accumulate in your body.
Back to the topic at hand: boosting performance with caffeine. Here it is in a nutshell. Don't use caffeine for a month before your race. Use caffeine as late in the race as you can hold out. This will probably be about fifteen hours into the first day. Use a small amount and wait for it to start wearing off before you have some more. Overlapping caffeine doses just wastes good stimulant affect. A good way to use caffeine in a race is coffee beans. One small bean goes a long way. Hold it in your mouth and suck on it for a little while.
Caffeine is a much more mild diuretic than most people think. However, it's still good to drink a little extra water to make sure it doesn't acidify your body too much when you're using it.
Remember it's the small advantages that make a successful race.