Vehicles with stop-start systems should not wear the engine out any more quickly than those without, because they do not operate until the engine is sufficiently warm and cold starting is the biggest cause of engine wear. Most engines with stop start also prevent the oil from returning to the sump, and even if your Fiesta does not have this system the engine is designed to restart automatically to prevent the oil from cooling too much and returning to the engine.

Your Fiesta will likely be fitted with an Enhanced Flooded Battery, which is specifically designed for the extra demands of stop start engines, while starter motors are also specified for the increased workload.