Myself and a mate did the canal in a day 2 years ago for a charity ride , it took us 14 1/2 hours and every mile from Skipton on hurt like you wouldn't believe , every time we stopped for a breather I curled into a fetus position on the floor.
We did the ride in the middle of July on a Sunday setting off from Liverpool at 6.45am. Most of the ride is pretty easy going , the section around Wigan is the only real climb but it's quite long (about 14 locks but well spread out). You need to go round the Foulridge tunnel but the signs are quite good. The section around Gargrave is a killer as there's about 5 miles of grass without a real pathway that really saps any energy you have left.
We took a break for 10 minutes every hour and 3/4 of an hour at the halfway point , nutrition for the day consisited of a good breakfast , 10 energy gels throughout the day and 3 peanut butter and banana sarnies at lunch. Despite copious amounts of vaseline being applied to my nether regions my perinium looked like some sadist had taken a belt sander to it and was sore for 3 weeks after.
If i were ever likely to do it again(no bloody chance!!) I'd definately do the food differently , it was a fantastic experience but it really took it's toll on me , but the 2 of us raised over £1000 for a local sick childrens charity so that made all the pain worthwhile.