I have had the Tire Minder system for 5 years. I have 6 removable cap sensors on brass valve extenders. It was at least a year before I had to change any cap battery. Replacing batteries in the caps is very easy. After about 2 or 3 years one of the cap cases cracked so I had to replace it. I bought the very inexpensive cap kit with multiple cases and O rings. After four years one of the sensors locked up at a constant reading. I replaced it. The receiver/computer has a learning mode to set up which caps are on which tire. The system has been very useful and reliable, has calibrated well against a high accuracy manual gauge, and requires no fussing. I read the receiver whenever I want and leave it on continuously when I am traveling to alert me when issues arise. The receiver is always plugged into power when I am driving. So far the receiver battery is going strong. The receiver battery is not replaceable.
I don’t use a sensor on the spare. I can add air when it gets installed and will use the bad tire sensor.
