The remote for the Presara is always active, as in it needs to send a signal out for you to enter and start the car. It depends on how often you use your vehicle, and even if you just leave the remote and never use it, it will still drain the battery, so it is a good idea to rotate the use of the two remotes you have, both of mine lasted for nearly 3 years. You could get them replaced at Toyota for about $23 or you could go to Jaycar and replace them for $3.95. (this has been posted in another topic somewhere) The battery is CR1632.