There are three things that seasoned tourists recommend taking more; clothing, food and water. Of the three I am most aware that it is hard to have too much water, especially in central Florida in the summer.
When I joined the Holie Pokies (cause that's what it's all about) for my first group ride I rode more than fifty miles for the first time. I carried three 24 ounce water bottles in cages and a fourth bottle in a pannier. I needed all I had. Thirty years ago when I was still capable or running, I learned the value of hydration in advance of hot weather training, so I always drink a lot of water and other fluids. Riding the 22 or so miles with the group was easy as their average speed seldom exceeded thirteen miles per hour. Riding the fifteen miles back home from their meeting place was not so easy.
Since then I have upped my mileage so I can cover fifty miles without undue stress. Four water bottle cages allow me to carry three 24 ounce bottles and one 16 ounce bottle. I drink all of it and often a fourth 24 ounce stashed in one of the panniers. As I increase my base mileage I will carry more than one extra bottle at the rate of 24 ounces per 10 to 20 miles, at least.
There is a second less obvious element to water. When I rode the final fifteen miles home after doing the Hokie Pokie, I found the final bottle of sun-warmed water was a link to a practical reality. I believed I could make the final 15 miles, but it was only when I lifted the bottle and took another mouthful of water that I knew I could. I was really tired!
Maybe it's too much like some kind of cosmic consciousness to revere my water bottles, but, damn I am glad to have lots of them. I like to pause in my cadence, savor the warm stuff and take a moment to relax. That something basic and simple can contribute positively to my bicycle adventure reaffirms the value of doing something basic and simple to improve me and my world.