求翻译：9. 甲本协议书有效期八年,双方自签字之日起生效。有效期期满后，如甲、乙双方无任何一方提出书面终止合约申请，此合约将默认自动延期。是什么意思？

9. this agreement is valid for eight years, the two sides take effect from the date it is signed. After expiry of the validity period, such as the a and b both sides without any party to apply in writing terminate the contract, this contract will default automatically postponed.