Are there any tell-tale signs that a starter motor might expire soon?
Starter motors do have a habit of quietly going on "strike" without any warning. There is not much you can do to avoid such a situation since the starter does not have a documented lifespan.
Even for one specific car model, there is no pattern to identify exactly how many years it will last or at what mileage it will fail.
In most cases, though, you will receive some signs that there is a problem with your starter or the electrical circuit of the starting system. The most obvious tell-tale sign is a lazy or slow cranking when you try to start the car.
This symptom, however, is not definitive in identifying the starter motor as the cause. It could also result from a weak battery or deteriorated motor cabling.
The starter motor is the highest consumer of the 12-volt battery's electrical energy, being a high-torque, high-speed motor that must turn the engine to its minimum self-sustainable speed of between 70 and 100rpm.
Most starter motors for petrol-engine cars are rated at about 2kW. Therefore, the condition of the battery and the main 12-volt supply cable is critical. Only after these two items are checked and confirmed to be in good health can you conclude that the starter motor is nearing the end of its duty.