good strategy is to mail the envelopes late on Friday or early Saturday. That gives your envelope a good chance to be in Harrisburg first thing Monday
That may have worked before they went to the WMU system but now the only thing that happens when you mail it in on Friday or Saturday morning is that it is the first to arrive and subsequently goes on the bottom of the pile in Harrisburg to be sent out to the county treasurers.
I am sending 4C first this year then follow up with 3D for the second round and 5C for the third. I live in one and the other two are less than 10 minutes from my house.
Thanks for posting this reminder. I try to do it each year a few days before the due date.