Yes you can renew the medical without even flying. If you are under 40, while the class 1 medical expires after 12 months, it is still then gives you a Class 2 medical for a further 4 years (5 years from the date of initial class 1 issue) . So you don't even need to renew the class 1 immediately at the expiry date, you wait until you need a class 1 again.