So yes, set up some scripts, you can go back 90 days from when you file (you get a grace period). Also if you're publishing frequently to a blog, repo, or newsletter, you can save cost by filing each article under a group registration. Ping me if you need help.

There are tens of millions of registered copyrights in the US, nearly every published book, music, artwork, many magazines and major websites. Here's the official link, you can search the registry and there is a ton of info: https://www.copyright.gov/registration/