Backup New Blogger template PLUS Page Elements and changing to another New Blogger template
How to backup New Blogger Page Elements
you may lose a lot of things when you revert to the old classic template to get that template. By saving a copy, you need not revert to the old classic template to get the previous old classic template before you upgrade. In any case, why only depend on Blogger. Why not keep a copy yourself and be under full control of your own template? It also serve as an extra backup in case anything happen, and there is only good that can come out of such a move.
A further reason why you should do the above is, you can have easy access to whatever customization you may have done in the old classic template which you will lose when you upgrade to New Blogger template.
An example - the "blogroll" or Link List. In the old classic template, it is in the form of HTML for an unordered list plus hyperlink HTML tags. I give an actual example below which uses the title "Blogger Resources" (which, I am an eternal optimist, I hope someone who find blogs like this one helpful, plus wants their visitor to have access to the same kind of information and/or help they get from this/these blogs, will add to their blog, with deletion of whatever they don't want of course:
Preferred method of adding Link List (blogroll) to New Blogger blogMost less knowledgeable bloggers will use the Link List Page Element to make their "blogroll". My advice is, don't, if you can help it. It is good if you don't want to bother with HTML (which is not difficult to learn, especially if you read sufficient number of posts in my blogs, but that Link List Page Element cannot be backed up. Something happened and you are forced to fall back to your backup template, your Link List is gone, no more. You will have to recreate it from scratch.
Note: target="_blank" had been depracated (mainly because of those darn mobile divices like hand phones that can display web pages, etc), and so don't know how long that is going to last.