Flashing "thanks" whether you needed it or not was a courtesy used my most on the highway a few years ago. About 50% of the truckers still do. Most RVers do not and I just assume they may be busy controlling their rig and write it off. I personally appreciate it, but do not depend on it. The one who really honks me off is the guy who decides because he flipped his turn signal he can cut in front of me to let a truck on the super slab when there is very little room for him. I do not like that, I leave enough room for emergencies between me and the guy in front of me, this guy plugs it up.