If it's really hot, I don't care - I'm wearing my faux camelbak. They're not that heavy and they keep the water VERY cold for much longer than bottles. I'll refill my bottles from the camelbak whenever I need it. I can also unload my jersey pockets into it, so it's a sort of win-win.
I usually go through one bottle to the shack and another to the village, but it's nice to have non-fountain water for the return trip. I only drank one bottle going to the village last week, but it was pretty cold.