Final answer:
For a pilot over 40, Second Class Medical Certificate privileges last for 12 months, after which they default to third-class privileges.
Step-by-step explanation:
The duration of Second Class Medical Certificate privileges for a pilot who is over 40 years old is 12 months. After this period, the certificate's privileges default to those of a third-class medical certificate, allowing the pilot to use it for operations that require only a third-class medical certificate. This is specifically designed for pilots engaged in commercial, non-airline duties such as commercial drone operations, flight instruction, or charter flights.