We're working with dirty forms to at least warn users before they leave an unfinished page before they save. It kind of works. Would enabling revisions control work? At least in that case an admin could recover the last version. Is there an automatic autosave ... say every 30 sections -- to be sure work is properly saved even if the user forgets to hit save?
The Autosave module automatically saves a snapshot of your content type form using AJAX. If the user's browser or machine dies while editing a node; the edits will be presented to the user the next time they return to the node. The user may toggle back and forth between the last saved version and the version with the edits that were lost and select which of these they would like to continue with.
How often a form is autosaved as well as which content types to enable autosave for are admin configurable.
There is a Drupal 8 module: Autosave Form
We have tested it. It basically works, but is not stable and has open bugs for complex forms.
The "Autosave Form" module provides an autosave feature for all forms (entity forms inclusive). Currently the autosave submit will be triggered every 60 seconds, but this approach might be exchanged later through a solution listening for DOM changes.