I agree with Steve that if you carry 12 lbs. of water plus container, you are driving stakes into the heart of your trip.
I carry 4 L from Trailside Meadow up. This is the midway point to the summit and where I stop to eat before going higher...I have a tendency to lose my appetite above 12,000' when I am stressing out my body. If you have no experience above this level, I would suggest you stop Trailside Meadow and eat.
