I'm pretty set on my water ways, because I tend to travel quite fast.
Even on a week long trip I carry only a 1 quart army canteen in the summer and fall, because it's easy to drink from.
In the winter I carry a 1 litre Nalgene widemouth bottle. The widemouth because it's easier to fill up with snow than a narrow mouth drinking top. And then during the day, the heat from my pack melts it a bit and I'm good to go.
Generally I fill the bottles up in the morning, and along the way as I go. (I also have a water filter in case any water I see doesn't look safe) I try to practice water-discipline as well, drinking enough to stay hydrated, but not so much that I get an upset stomach from too much water on a lunch break.
At the end of the day, when I set up camp, I always make a brothy soup, like a Lipton Instant Noodle to replenish the salt I lost during the day, and to drink something warm. Then I reflect on the passing day before moving into dinner. (I think it's just like you British guys and your tea at camp!)
I don't think carrying three bottles is necessary if you have your cooking pot for your stove. But hey, that's only an opinion!
Cheers mate,
Adam