Useful tip. You can still drive the car with a dead fob key battery.

Unlock the car with your Smart phone App.
Place the dead key on the bottom of the central storage bin, right at the front.
You should then be able to put the car into drive and drive off.

Booked into dealership - new keyfobs supplied. Watch and wait!

SInce buying my #1 in September, I have replaced the batteries in both key fobs 4 times! Both batteries run out at the same time without warning. The manual state you should get a low battery warning - I don't. I have been caught out away from home where the key fob has stopped working and I've had ...

There is indeed a legal requirement but I agree, it's really annoying. Interestingly Mercedes, the parent company, have a small icon on the home screen which you can press to deactivate the bleeping without having to delve into variuous menu sublevels. Admittedly, it still needs to be done each time...