Have you worked out your nutrition and hydration strategy?
It's a good idea to do a few long training rides in the lead-up to work out what you need for carbs and hydration. Getting caught short in either department, or (worse) locked up with excruciating cramps in the middle of nowhere is not fun - best avoided!
Let me state emphatically that Gatorade or similar lolly water does not cut the mustard unless you are into self-inflicted misery. Sucrose (standard table sugar) spikes and then dumps you straight into bonk-land. Most unpleasant.
Sustainable race pace is around 75-90% of threshhold heart rate, and you should aim to consume 1-1.3g of carbs per kg of bodyweight per hour. For me (AT) 80kg, that's one bidon of High5, + one High5 gel + half a soft fruit bar per hour. 2:1 Maltodextrin - fructose mixes like High 5, Endura and GU2O are far far better. For 6 hours I'd even be looking at something with protein in it like Hammer Heed.
Oh, and while I remember, don't put these mixes in your Camelbak bladder. Impossible to rinse out properly and ghastly bacterial growth is the result.
Bottles only.