Hydration needs vary like everything else in life. Everyone needs to drink as much as necessary which you need to determine for your self. I used to weigh myself before a ride and then after the ride. The idea was not to complete a ride in a serious deficit which for me was a weight loss of no more than 1 or maybe 1 1/2 pounds (half a liter or a bit more). These days the weighing is no longer necessary except now and then as a check. In the past for a ride of five hours or so I would need nearly 3 24 ounce water bottles in my area. these days 2 24 oz. bottles is enough. Coastal Rhode Island and southern Massachusetts is cooler than further inland. If I lived in a hotter climate more hydration would be called for.