I'm on my third E-ZPass tag. The battery in the first one died after about 5 years. I have had the second one for another 5 years. This time, the E-ZPass people sent me a new one before the current one died.
They did it the right way. The new tag came in a small envelope with a letter and a return envelope. The return envelope was for the old tag so it could be sent back. It was a pre-paid envelope, a nice touch. The letter explained that the new tag had to be sent back, or I would be charged for it's replacement cost.
They clearly labeled the serial number of the old tag and of the new one. I have two tags in use, I had to check each car to grab the right one.
The replacement tag had a eaisy to peel off sticker with the following text: THIS IS YOUR REPLACEMENT TAG. Seems kinds of obvious, but if you are fooling around in your garage with the tags, that makes it easy not to mix up the old tag with the new one.
They could have mentioned which car the tag was for. The only way to tell was by the serial number on the front of tag. I could read it just fine, but it's in small print and that's not too friendly for AARP crowd. That would be the only thing I would have changed with how they handle replacements.
More companies should study how the E-ZPass program is run. The hardware just works, no fuss or muss. We recentl;y drove from Albany NY, to Corolla, NC and just about every toll bridge and road accepted the E-ZPass. The only exception was the Chesapeake Bay Bridge-Tunnel, and they are in the process of implementing an electronic toll collection system (E-ZPass).