NSN and on the service cross write, "Duplex does not have unit numbers."
Of course that would depend on the location. Near the college, I would do that every single day of the week, in a small town, I would probably leave it, knowing that the correct person would eventually get it.
A while back we had a clerk AC stuff to a wrong address in a very small town. After about 2 weeks, the guy called in a concern about getting all this stuff. He said that he did not have time to call everyone and wait for them to come over and pick it up as he had been doing. (all the stuff ACd to him was sure post stuff that had a PO address, but the PO was closed, so we delivered all the stuff in that town.)
I made it a point the next day to stop at his house and thank him for doing what we should have been.
He said, "Bah, it's just what people do when you know everyone in town." and he laughed.
Address corrections require a signature around here