Register and create an account on freemindshare.com. This will give you a non-restricted lifetime access to your online mind maps (compared to just one week for an anonymous account). This will also enable you to protect your mind maps with a password.
This service is supplied free of charge and without any obligation.
Bear in mind that the FreeMindShare service IS NOT A BACKUP service. We DO NOT COMMIT TO ANYTHING regarding the availability or reliability of your maps. In case of an incident - e.g. server crash, network unavailability, or any other failure - some mind maps may become unavailable or even be deleted. Nethertheless, we will do our best to offer a service of quality and act so your maps remain available, and perform regular backups on our own.