Look into lgogdownloader, it’ll automate that process for you and it’s really convenient, and skips ones that are already backed up in future backups.

I run it every other month or so

Edit: ah just realized it’s linux only, I’m sure there’s some version of the same thing for Windows and Mac too though

Edit 2: here’s one that should work on Windows and Mac too https://github.com/Kalanyr/gogrepoc it’s not the most user friendly but worth it if you have way too many games to go through, especially for those that break up the offline installer into like 20 different 4gb parts per game