mail forwarding

We've been doing the temporary change of address to PO Box in the south for about 12 winters now. About half of those have gone smooth. The rest have had a problem. For those of us that hold a PO Box year round when our stop date comes they tape over the back side of the PO Box. We have had years where our mail started coming to the PO, but the tape was still on the box so they sent the mail back north. One winter we had mail go around in a circle for over 3 weeks. The fix to the problem is now I call the post office down south and ask them to open my box, which you should not have to do.