Every subscription contract made by a vision service plan corporation shall provide for the payment of vision services for a minimum period of twelve (12) months from the date of issue of the subscription certificate. The contract may provide that it shall be subject to renewal thereafter from year to year unless there has been one (1) month's prior written notice of termination by the vision service plan corporation. A subscriber shall forfeit membership upon failure to renew the contract, or upon voluntary resignation. During the first contract year, the contract may provide that the inception coverage may be deferred for not more than two (2) months from date of issue of the contract.