Steam shows ~800 hours for me but that's before I went all-in on various mods and just wrote my own launcher for easy switching between mod packs/saves/etc so thankfully I don't have the full numbers (though the vast majority of my playtime happened after that change so I know I'm probably around your number).
The install is completely portable on its own, so my solution is that I just have 10 or so copies of the game installed, with a folder of renamed shortcuts based on the modpack they run.
Nothing special, it’s an Alfred workflow to list my installs which are just folders on the file system. Each folder has its own saves/mods and a link to launch the version of Factorio I want. It calls a script that symlinks the mods/saves to the right place and launches the game.
