Sorry, over last months I had no time to work on the plugin, because I had to focus on the Jenkins core and other projects. I also have not been using this plugin on my own since 2016. So I have decided to unassign the issues so that there is no expectation that I work on them anytime soon.
Currently the plugin is being transfered to another maintainer. Hopefully he will have some time to finish triaging of the issues and maybe to deliver some fixes. But, as in any community-driven project, everybody is welcome to propose pull requests and to contribute to the plugin's state.
I am not sure I understand the issue. Setting Keep Forever is an option step for the promotion. Is the request to make the default keep forever for a promotion? That doesn't seem wise.