Backing up your Blogger blog even if it is once in a week is highly recommended if you really care about your blog. Although Blogger blogs are not easily hacked but Blogger can disable or delete your Blog without warning you. Mind you, Blogger automated classification system can disable your blog without you doing anything wrong. I experienced this recently.
If such happens and you have a back up file of your blog, you can easily create a new blog and restore the content of your old blog. Besides, if you decide to move to Wordpress, the .xml back up file is all you need to restore your blog posts and comments to the Wordpress blog.
Backing up your Blogger blog is very easy. You can get it done easily using the "export" feature of Blogger. The Blogger tool lets you save a copy of your blog on your hard drive. The export tool will not back up your Blogger template though, just your posts (including drafts) and comments.
==> Sign in to www.blogger.com
==> Click on the Small arrow beside the "view blog" button
==> Click on "Settings" > "Other"
==> Click on the 'Export blog" link under Blog tools.
==> Click on 'Download blog"
==> Save the .xml file to your PC
You can rename it to include the date your backup and you can upload it to the cloud eg to dropbox, Google drive etc so you can always access it from anywhere whenever you need it.
The total number of posts and comments will determine the size of the export file.
Remember, your data is very important. So, DO NOT download your back up on public computers.
You can use Google TakeOut to back up all the blogs in your Blogger dashboard and if you want to back up the design/look of your Blogger blog, read how to back up Blogger template.
When last did you back up your blog?