It's like switching a traditional light bulb on and off in a continuous way - it won't last years (some 100+ old light bulbs still work fine, but the were powered-off just a handful times).
http://www.autocar.co.uk/car-news/new-cars/stop-start-long-t...
While a home light bulb may not stand up to continuous on/off cycles, a bulb that's designed to do so (like a low-voltage bulb with a heavy filament) can last for a very long time.
So I wouldn't retrofit an existing car with a start-stop system, but I wouldn't have any qualms about purchasing a car with a start-stop engine as it would have been designed for the purpose.
Yes, that too. Although I imagine it would wear out certain components of the engine (such as starter-motor, and crankshaft?) and battery rather than the engine as a whole.
Total-Cost-of-Ownership-wise, a stop-start might save more in fuel than it would cost in increased repairs (Or it may not, depending on make and model among other things).