I think I have mentioned this before - check with your insurer before disabling the tyre pressure sensors since it is a manufacturer's fitted safety device. In the event of any tyre related accident it may be that your insurance is compromised if the system is disabled. The sensors are ok when working but there is a strict routine to follow when changing tyres i.e. the rubber grommets should be changed as per Schrader's recommendations each time a tyre is changed otherwise there will be air leakage due to the grommets perishing ( a common occurance). Battery life is quoted as 10 years (longer than the life of the car!!!!).