If you buy a quality leather jacket it will last a lifetime with proper care. just do not let the leather dry out. Yearly leather conditioning is a good idea.
Cheap leather jackets will fail sooner because the leather is cheap. A lot of cheap leather jackets are not real leather but chunks of leather formed into a substrate and will a polyurethane top coat applied which will peal over time.
Be careful about the rain: leather is permeable so if it get very wet it is important to dry it in a ventilated place without direct exposure to the sun.
