This is so true BUT I do believe in hydrating the entire day. I try to ski non-stop(or maybe just a few minute breaks) from start until about 2:30-3:00. I bring gu's, fig bars, powerbars in my bag for nutrition and an extra layer if need be and a few other things too. The downside is I do need to stop a few times for a "nature" break. I ski Mammoth mountain mostly and you have to walk by the bathroom on your way to Gondola any ways so it's no big deal.
I see this as a perfectly^ reasonable attitude; it always cracks me up when people carry water on their back but still get dehydrated because they're avoiding the need for nature breaks.