I did it going into the grand canyon. I had a bunch I got for free that I needed to get rid of. Luckily I had a pretty good variety of flavors, which was the only thing that saved me.
It got to the point that I would have a blueberry cliff bar as desert. Thats just sad.
One piece of advice, if you must do this, don't buy chocolate ones. If its just chips that should be fine, but my friend who also did the cliff bar meal plan had brownie, chocolate fudge, and chocolate chip I think.
Watching him eat was one of the funniest things I've seen. I think it was harder for him than the hike.
I did a half cliff bar plan on another hike. But also brought along a thing of salami, some almonds, and dried mangos.
Having real food-even though it is noncook- is so much better than straight cliff bars. There is no reason to put yourself through that. Especially if you are going with other people who aren't eating only cliff bars. You will be so jealous that you wont want to eat.