[quote=porta]My float tube is kept at low pressure, just enough to hold shape and then topped off with a mouth tube just before launching. This helps it last longer, because there is less stress on the bladder and fabric seams compared to storage at full pressure- plus hot days can make the full pressure go over recommendations.
(This is what I was taught to do as well. Float tubes are really popular back in my native CO and we always air them down, not just for the heat but also to elevation change. Where I grew up was about 6500 feet but I did a lot of fishing over 10000 feet and that makes a difference.)
Flags, the cold snow melt during Summer at altitude can also be a consideration. Sometimes I've had to add pressure with a mouth tube after 30 minutes or so of floating, and then remove that same pressure when getting out of that cold water. Tubed a river at Lyons many years ago, during a good flow, found some good fishing holes! My tube flies with me sometimes....