Simple Summary
This is an idea for Expirable NFTs, which extends ERC-721.
It is called Expirable Non-Fungible Token (ENFT) to provide potential NFT lending use cases.
Abstract
The ERC-721 is mainly used for transferring digital or physical assets and transfer interface does not have any expiration date.
Meanwhile, there are some potential possibility of lending NFT such as digital book as NFT which a digital library could lend to person for a certain period. A NFT owner might lend his/her collection to other party momentarily. Or even 1 year real estate rental.
With ENFT then when the expiration date is due the NFT temporary ownership will be revoked and the original owner will re-own the digital or physical assets.
The ENFT does not consider combining lending condition contract (usually happens in physical world) at this moment but it can be expanded in the future with combine support of lending contract.
Summary
The ENFT can be considered as extention of ERC-721 which adding expiration date to support a temporarily ownersip will be expired in future date.