Would you be willing to describe the process you use to do this?
* when setting up 2FA, a website shows a QR code
* I screenshot the QR code, and print it out on an A4 sheet, with an annotation of what service it is for
* I scan the QR code from the A4 sheet on two different phones.
* Back on the website, I continue 2FA setup process only after the A4 sheet is printed, and both phones show the same codes
* The A4 sheet goes in a folder for safe keeping
* One phone goes in my desk drawer for daily use
* The other phone goes in my "go" bag that I take with me on short trips etc.
Both phones are used exclusively for Google Authenticator:
* they have no extra apps
* they have a screen lock
* they are always in flight mode
Started doing this when I got burned by having to extract GA's sqlite file from mostly-dead Nexus One over adb.
The app puts a no screenshot request, so you have to scan the qr code from another phone.
Without it, he has 30 seconds to login and put the code by just opening the app and looking at the code.
Not much of a feature, but might help some users