You should always have a backup of everything you do online as you never know when something could crash and wipe your data. Exporting MailChimps data is very easy.
This will allow you to put all your data into a CSV file which will contain your campaigns, subscribers, lists, and reports along with your saved templates.
MailChimp bundle them into a single zip file for you. This may take a little while if you have a lot of data.
So to do this, simply sign in to your MailChimp account and select the drop down menu on the right hand side and click Account.
On this page you can select Account Settings > Export my data. It will then allow you to export your data at a click of the button. The data will be sent to your email address, it will state what email address you will receive it at.
MailChimp also states only one backup can be completed every 24 hours, so backup your data once you have completed your days work on your campaigns, lists uploads and so on.