I frequently ( once or twice a weekend) hike 3/4 miles with a tube on my back in the GA sunshine, after driving approx. 12 miles in the start point of the hike. When I was using a round tube with a 10.00 x 20 intertube in it I pump it up once or twice a year with an air compressor. I switched to a LCS4 with bladders last year and will top off the bladders with lung power before starting my float down the Hooch. I have a pump but that's a couple of more pounds to carry 3/4 mile.
Several year ago up in Gemrod's neighborhood, I witnessed a round tube explode as the owner was about to enter the lake. We figured he air it up down on the flatlands before coming up to about 9,000 elevation.
I don't remember the physic's laws regarding the expansion of gases but I under the principles. Like gravity, they are very reliable.
