You only need to backup your Secret Phrase once, it's best to do this as soon as you create a new wallet.
Secret Phrase will not change, so you do not need to back up when the application is updated.
The best way to back up your Secret Phrase is to write or print them down on paper.
You can also copy and save them on your computer or take a screenshot for archiving if you don't have time to record it yet. However, this way is not recommended, because digital data still has the potential to be attacked.