For sure: if you've lost all your fingers & thumbs or even have had your arms amputated above the elbow, use a gauge. Otherwise if you own an inflatable and can't tell when it's approaching over-inflation, pay more attention.
Seriously? Folks will invest thousands of $ in a rig but can't tell when their boat is gaining pressure? Approaching over-inflation?
If your boat is in the water - not pulled up on shore, but floating (which is what boats want to do) - there's nothing to worry about. Period. If anyone on this forum has ever witnessed a boat exploding DUE TO OVER INFLATION WHILE FLOATING on the water, I'd really like to hear about it. I imagine the physics of gaining buoyancy are possible given today's great big tubes and really, really hot temps - like below Separation in June/July - but I've been there, done that (a bunch), and never seen or heard of it.
Elevation is another story. Pay attention to expansion as you go up with a boat on a trailer - but I don't know of any rivers where the put-in is lower than the takeout...