It does not need to be replaced. The battery is a simple watch battery, you can buy them anywhere.

That's what I would have expect and that makes a lot more sense. I have the "intelligent key" in my Infiniti and after a little over 2 years and 38,000 miles, my battery seems to be dying (car has been telling me so for a over a month now), but continues to work.

The battery in the comfort access remote is not rechargeable - is not impacted one way or another by inserting in ignition slot.

All rechargeable batteries eventually die. They can last a long time if charged properly.

The battery has what they call a memory and that determines how much charge it can hold over time. Improperly charging or lack of charging can cause the memory effect and thus... decrease how long the battery will be serviceable.

You are supposed to charge both keys fully at least once a year. So if you are the only driver... you need to break out that spare or the battery will eventually fail.

Placing your remote in the dash allows the car to charge it when necessary. People with the comfort access remote will almost NEVER place it in the dash and then not for that long. This is why they do not get a rechargable remote. They can replace the battery every few years and not have to worry about it.

Your key will always work. If it has an RFID chip.. the car sends out a energy signal that powers the RFID to transmit a code. The car then knows it can start.

The remote may hold just enough power to lock or unlock the doors but eventually... it will die completely. You can still start the car with a dead remote battery.

The remote should be covered by your warranty if one exists.

Read the manual ;)