For me it really depends on the course and the weather. I always carry two bottles, with my needs determining the size. Getting to know the areas one rides in and all the good water stops helps. If I know I might need more on a section of the route, I'll get a small bottle from a service station before starting out and put it in my bag or jersey pocket. Depending on conditions, I normally go 40 - 60 miles on two bottles. And if I do have to stop in between controls, 2 minutes is really of no consequence. I rarely need to pay for water. Most service stations that have a convenience store don't mind if you get water from the soda fountain but may charge a quarter for ice. Parks almost always have a spigot or fountain. The restrooms at the top of a favorite local climb have sinks deep enough to fit a bottle under the tap, so you can get for free the same well water people are paying a few dollars a gallon for.