I havent changed mine yet. This past season was the second season for them. I tested the output of the batteries and they seemed good so I didnt change them. I did take the batteries out of the sensor though for winter storage too maybe that helps?
Reason I asked, I just bought a set off of Amazon. The price was right. Five of them shipped here for $5.39. They are in the original sealed package, but the date is 2010. I've read quite a few of the reviews, and everyone seems to be satisfied. So we will see.
I changed mine just before out big trip this last summer as I didn't want any surprises on the road. I got my batteries from Amazon also and while I didn't check the date they worked as advertised.
I do have one sensor that has failed and need to get it replaced. I hope that's not an indication of things to come.
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Ken and Marilyn, 2010 CF30SK, 2003 F250 V10 www.runnerduck.com