At Planio, we hosting Redmine professionally. Whenever our customers ask us to install a specific plugin they've found in the plugin list, our team conducts an extensive stability and security audit and will only install a plugin if it's safe for production use.
If a plugin is no longer maintained, we also maintain the code ourselves and contribute the code back to the community, usually via GitHub. We've been doing this for quite some time now.
We published a list of Redmine Plugins which have passed our checks and we are planning to keep writing more plugin reviews as we go using the Redmine Plugins tag on our blog.
You can read the article here: Redmine Plugins: the Planio-Approved List.
So, if you've found a plugin for which you may not be sure if it's production ready, or if you cannot use a given plugin with the latest version of Redmine, check out our list and/or GitHub account. We might have a newer/compatible version for you – no Planio account required.
Hope this helps!