The average life of a motor depends on the type of motor and how well maintained it is.
Gasoline motors in cars and vehicles often last 200,000 to 500,000 miles and sometimes longer which could be 10 to 20 years or longer.
Diesel motors often last for 800,000 to 1 million miles and sometimes longer.
Electric motors if well maintained can last 10 years to 20 years or longer.
If it's an electric motor that runs off household power then as long as it's maintained and the bearings are oiled or greased often enough it can last decades.
If the bearings are not oiled or lubricated or greased the bearings can wear out and the motor can overheat and it could die within a few years.
If it's a car engine or vehicle engine and is a gas or diesel engine it should last several years and several miles as long as you change the engine oil and oil filter every 3,000 miles or so.
Not changing the oil and oil filter often enough is a major cause of the engine or motor failing in a vehicle sooner than it should.
Also you should check the oil level often because if the engine develops and oil leak and the oil level gets too low it can too cause the engine to seize up.