An old manager of mine's backup solution was a cronjob that appended .old to every file then made a copy of the most recent one. So he had:
file, file.old, file.old.old, file.old.old.old, ...
I like adding a backup function to .profile that can take a file or list of files as an argument and make a copy with a date suffix on the file name, and same date additional backups just add a character like ~ at the end. It's in version control, but if I'm testing a change it's just faster to restore the file from a copy in the same place.
Obligatory note that /etc/profile and ~/.profile are only run by login shells, and many terminal emulators do not execute a login shell by default.
Unfortunately, there is no standard secondary place* that all shells execute, so check your chosen shell's manual for what it does run on startup and put your functions into one of those. Preferably one that goes in your homedir.
Alternatively have that file source ~/.profile assuming that won't cause an infinite loop.
* And not even a primary if you count *csh, but if you use those you have other problems.
People here really hate our distro for some reason. Isn't it just Arch with extra steps (and all the configs in one file)? Everyone likes Arch! The definition of Arch is extra steps!