I would just like to bring an older issue to the fore. This has been discussed on the mailing list (http://mail.scipy.org/pipermail/ipython-user/2012-January/009160.html) an in one of the issues it is also mentioned (#977), but I couldn't find an issue for it. I hope it is OK to raise again.

The consensus on the mailing list seemed to be that a simple autosave would be useful even before the implementation of a full-fledged revision control system, and it should have the following features:

1. For a start, the timeout would not have to be configurable, something like 5-10 minutes should be OK.
2. The backup file for foo_notebook.ipynb should be named .foo_notebook.ipynb, so that it is invisible, but can be loaded as normal notebook, when recovery is necessary.
3. Backup files should be removed on clean exit.

Are these criteria still OK?