If that were the case, wouldn’t the red ‘battery low’ light be on? It’s never been on.
Mine didnt come on. But both times over the years when the obnoxious beeping starts it’s been the battery. I got FIOS to replace the first one after pointing out that I didnt buy the device I paid them monthly and no where on their site did it say I had to buy and replace battery. It did this last time.