When I go to the range I always check the chambers of my firearms before I ready them for transport. I check them again when we arrive. I explained to my son that even though I KNOW the guns are unloaded I am trying to reinforce a personal habit. Since the guns were out of my control for a period of time I check them. That's so in case some day if I prep a gun for transport and someone comes along behind me and messes with it I'll check to make sure it is unloaded rather than assume it is.
Anytime I handle my HD handgun I do a brass check. I don't keep a round in the chamber for safety reasons. Hell, I don't even keep a magazine in it, just nearby. I still do the brass check.
I had a negligent discharge over 20 years ago with a .22 rifle when I was sure I was being "safe". Call me a Safety Susie, but I learned how just one moment of overconfidence very nearly put a hole in my foot. I'm working hard to make sure my sons don't ever learn that lesson the hard way.