Thanks everyone for sharing your perspective and your experiences.
I ran an 18 mile run today. But only had 22oz of water and 1 gu gel during the run. I definitely need to up that. There were water fountains along the way but i skipped because I did not want to stop :P
I was tired but not dying at the end of the run and could have gone few miles more .
18 miles in 2:37 @ 8:43/mile
Have a 20 miles and another 18 miles long run in next 3 weeks after which I will taper,
Will keep you posted.