Originally Posted by jpristel
You'll know when it's going to cause you problems, because you'll start to loose the range you typically have to unlock your car doors. However, if you're like me, you might start trying to diagnose ignition failures before finding out that this "failure" is actually a "feature".
If my batteries have been in the FOB for much over a year, my first diagnostic step would be to put in a fresh set of batteries. I'm in the habit of swapping out batteries on the anniversary of the purchase date or there abouts, no problems so far. And as preventive maintenance, I faithfully change out the main car battery every three years... why wait for a dead battery?