From award winning package author Matthew Begent and Gibe
Sick of clients complaining about losing their work? Tired of writing a long blog post only to lose it all because Umbraco has logged you out? Introducing Drafts, a gmail-like Umbraco native saving experience. Never lose your work again! Use at your own risk, no warranty included, you may not gain back all the words that you type in.
https://marketplace.umbraco.com/package/umbraco.community.drafts