It's all about the Fob Batteries, followed by actual battery. They don't like being left unused and get very grumpy if they are. It's a year since I changed all three but the time is nigh for fob battery change again. A low cost precaution to what can turn into a real faff. Mine is a November 2016 A124, so adding a couple more fob batteries to the annual costs bill is only a couple of missed coffees at Costa or Starbucks!
I definitely agree that a lot of weird behaviour with the keys is most commonly solved by a simple battery replacement. This should always be the first port of call. However issues should not and to my knowledge can not arise by the fob being left unused or left to go dead. They are very resilient devices in their design and the design of the fob which is a Mitsubishi unit is used by a huge population of cars and manufacturers across the world. If the fob were the issue we would know about that, and it surely wouldn't be an issue for long.
In their keyless function all they do is listen for a wake signal on low frequency (Which only travels a few metres in clear LOS) ~125 KHz and respond over 433MHz /315 MHz (depending on your country) with a code, which is picked up by the car. Allowing it to initiate the ignition. The code is picked from a really long "list" that comes pre-programmed on the remote from the factory. The wake signal sent out never changes for our cars. And so the signal the fob is listening for is also pre-programmed. Meaning there is very little to go wrong. And its basically impossible without damage to the remote for it to forget the "list" of codes. (It's not an actual list its an algorithm that runs nowadays). This system is a microcontroller based system, in other words, extremely reliable and consistent.
In my opinion these issues arise from the car no longer recognising the codes and the signature of the keys. Not the other way around. Definitely not just from the batteries of the remote going dead. It's possible for damage of the fob to cause it to no longer to receive or send signals but the chances of both keys failing at the exact same time in the exact same way are astronomically small. Even smaller still for a failure of that kind to be caused by a dead batter.
I feel like you meant well with your comment but it doesn't help to perpetuate myths even if in your personal experience the cause and effect seem to align. I just wanted to clarify this point because I've done an immense amount of research and my own RF testing and validation on my remotes and car. Mainly because I absolutely hate the lack of transparency of modern day dealers and mechanics. No one is willing to give you a straight answer which leads to tonnes of headaches and speculation on forums just like this.
