I did. Then I forgot to insert sd card one time before powering on and fuse was burned. I think I had a backup of 3.1? and after I had 7.x. I've asked here if I can still go back to 3.1 but never got a clear answer so I gave up.
Well crap.
If you have 5 or more fuses burnt you can’t go back to 3.x without running Hekate and it ability to skip the fuse checking/burning algorithm from Ninty. If you have 10 or more burnt then 7 is moot too.
Here’s some more info on the matter: https://switchbrew.org/wiki/Fuses#Anti-downgrade
It’s still good to keep those backups…if anything ever happens to your Sysnand you can overwrite it with your old version and use Hekate to boot into Atmosphere and then use Daybreak to update your FW to latest.
It’s a bit of a convoluted path but you won’t ever be completely bricked (From this specific use case…there are probably other ways to screw the pooch.)