Yep. I think its important for project maintainers to be clear about the maintenance status of a project. You don't have to maintain a project forever, but if its not maintained its good to be clear about that.

Eg: "This project works but will not be maintained. Github issues & PRs will be ignored. If you want changes, fork the project. If your fork is being actively maintained, let me know and I'll link to your fork from this readme."