Well, it's true that if you're p&g'ing it, the loss isn't nearly as great. It's not like you have a choice to run lower rpm at that speed, so make full use of the power that's there.
It's kinda fun, too.
All my routes have driveways and cross streets along the way, so there's no minimum limit.
I'm not sure our ideas of "lugging" are the same.
At low loads I take it down to even lower rpm.