My wife just bought a new Mercedes. At red lights or in heavy traffic the engine shuts off and re starts went the brake is released. She was told by the dealer this is a gas saving feature. How long before the starter motor gives out? Will the cost of gas saving account for the starter replacement cost?
The starters have been beefed up to handle the additional wear.
Yes, it is.
Probably not (because gas is cheap and Mercedes service is not), but as @old_mopar_guy posts, the starter is beefed up for this.
These systems are all designed to do just what they do. Now if you really are worried look in your manual to see what you have to do to turn the Stop/Start off. That will need to be done each time you restart the vehicle after complete shut down .