In the past we've only been gone two months max at a time and our PO has been gracious about extending our mail hold.
You do NOT need to suck up to your Post Office about mail hold or forwarding your mail.
Here is what I found out and do on line.
Go on line to the United States Postal website.
Plug in your PO box number or home address. Then click forward mail.
You put in where you want it forwarded to. CG or a neighbor or relative back home.
They will forward your mail automatically anywhere in the US for
4 months!
When the 4 months is up you go back on line and reapply for another 4 months. And so on if you desire. You can also stop the forwarding at any time on line if your trip is shorter than 4 months.