I've never, ever, heard of a fob completely dying. A dead battery, sure, but manufacturers took that into consideration - on our Volts for example, if the battery goes so dead on the fob to the point where they won't operate normally (IE, the fob just has to be inside the car but not in any particular place) then there is a backup plan - you open the little storage compartment on the dashboard, remove the rubber liner at the bottom, and place the fob in there - it's then close enough to the transponder in the car that it can apparently read the fob, even with a dead battery in the fob itself.
The car also starts telling you a month or so in advance of the fob battery dying that it's low....popping up an alert on the dash everytime you start the car.
This isn't new technology. Once you've had a car without a traditional ignition you'll think it's archaic technology once you get used to the fob-only setup. It's nice to be able to just throw the fob in your jacket pocket and not have to actually touch it at all from them forward.
There's also other advantages - for example, I have my wife's Volt setup to automagically lock when she walks away from it. The car detects it's lost communications with the fob and after 15 seconds, all the doors lock. Considering she used to have a bad habit of leaving her doors open all night (and probably during her daily routines, as well), this is a handy feature.