Water is heavy, I carry only what I need plus a small margin of safety. If I can get by with just two bottles in cages that is great. Unfortunately there are places where I have gone 80 or 90 miles with no chance for restocking. For those I fill my 2 liter water bladder and if necessary one or two recycled sports drink bottles. How much depends on the distance and the temperature. I try to camp near a water source, but often that is not possible. If I am carrying all of my water for longish distances I only use it for drinking and cooking, letting washing up wait until water is more plentiful.

In places where streams are plentiful and spigots not so much... I consider carrying a water filter. I only do that if it means carrying less total weight on a regular basis.