Welcome to the Buzz. I leave my boat rigged on a trailer year-round. There's a tarp over the boat at home that gets folded and taken with me on trips in case I stay at a motel or leave the boat out in public, so all that shiny expensive stuff isn't on full display. When traveling over passes, or if you start on a cool morning with the boat properly inflated and drive into the heat of the day, or the desert, the air in the tubes will expand. A lot. I'm always prepared to let some air out before heading up a big hill, or top it off again at the bottom, when traveling. I did some research once (prompted by a similar thread a few years ago) and found out that going from Denver over the Continental Divide, you increase the pressure by about 2.5 psi. So if your boat is properly inflated to 2.5 or 3 psi when you leave home, and you go another mile higher, then you're boat pressure is over 5 psi at the top. This is way overinflated and probably not good for the boat or your straps.
That said, I generally like to make sure my boat's inflated fairly tight to minimize how much it and all the gear rigged on it will bounce up against the straps going over bumps. Camstraps looped around the frame to the trailer is a lot better than rigging to the D-Rings, and you should never rig to the handles. I've driven tens of thousands of miles with my boat inflated on the trailer without any problems other than a little road tar once.
And like the others said, shoenfeld13 wasn't being an asshole, I'd say he was just being helpful and pointing out that there's a ton of stuff already written on the topic and that lots of folks have personal preferences. Here's another thread
with the identical subject line from last year where you may get a broader perspective.
Stick around, you'll learn a ton and meet some great folks.