Yeah, I've hit "the wall" a few times. The only hit the wall backpacking however a few times.

The first time was a few years ago in Alaska on my first backpacking trip while I lived there. Of course, work had me up at five in the morning and ruck marching out 5 miles on the crappiest rock road I've ever walked so we could go home for the weekend. I rolled my ankle over and over again on that stupid road and it had my feet burning, which is saying a lot because walking was the job pretty much. Then of course I had this trip planned for that day so it was get back to my room, change, grab my gear and buddy and dirve to the trail which was an hour away.

Then once we got to the trail, it was a 1,500 foot 5 mile hike constantly uphill until we reached the trail shelter, which we were determined to reach. We ate only once that whole day and by 10 o'clock at night(gotta love Alaska's long summer days for this reason) I was a walking zomby. It took us forever because my friend was a smoker and had to stop every so often as well, which was driving me nuts. Not to mention the trail was terrible the last 1 1/2 miles because it was climbing up rocks, hoping the rock cairns marking the trail hadn't been knocked over or anything. We pretty much stumlbed the last half mile to the shelter because we had been dumb about not eating enough not to mention we'd been up for a while as it was. That was a bad wall.

The last wall I did on purpose just to see where it was since I had had knee surgery 9 months earlier and had just got back into the excercise game a month earlier and hadn't dealt with the elevation of the Sawtooths here in Idaho in years. So I went a whole 6 or so hours above 7k-8.5k feet with just water until I hit the wall. Then when we stopped for water and to take a short break, I ate a protein bar and 20 minutes later I felt as good as I had at the beginning of the trail. On a side note, I really shocked the hell out of myself how easy it all was despite the short time I had to get back into shape.

So, given those two probably too long stories, yes, that energy stuff works. Keeping that glucose at a good level as much as possible will definitely help. I've been doing a lot of research on protein bars, looking at the nurtional stuff to see which ones will be the best for this upcoming season.

As for water, I've never drank more than a 3 liter Camelbak's worth of water and 1 whole 32 oz nalgene bottle of water in a day. Of course this is not counting the water I take in after I add the water to my food. So, as far as backpacking goes, no, I've never darnk more than six liters of water a day. It probably ends up being 5 liters at the most ever when all combined.