The idea of having notices dismissed for a given period of time is interesting. However, the process seems a bit fastidious in the sense that it is still necessary to manually create the notices.

Also, having to add long class names, and also not forget the is-dismissible class, looks like an easy way to forget something.

I have a similar library, available on GitHub since March, that automates most of the process. It also adds a couple more options for defining who sees what: https://github.com/julien731/WP-Dismissible-Notices-Handler