I think it would be foolish to think that GitHub will be around and be trustworthy forever. At some point it will go down like every other project does.
What is a good way to make sure I can still access my repos no matter what happens to GitHub?
I don't want to host them locally. Too much of a hassle.
What's an easy way to mirror them to other places?
git push backup master
My question is more about the where. What is a good free service that is expected to stand the test of time?
Maybe it's possible to make archive.org archive GitHub repos?
Just how long do you want?
Perhaps if you pay for a service it's more likely that it will last?
So I want to spread my code across multiple services. And when one goes down in 10 years or so, clone it from one of the others to yet another one.
Paying is not an option. Because I want a hassle free solution. Paid services would be prone to even more issues. For example when I change my credit card I would have to think about updating the CC information. At some point Credit Cards might go out of fashion. And the provider and I might not have a common payment channel anymore. Or the provier raises their fees to a level that I find too expensive.
I want a solution that I can set up and then forget about it for as long as possible.
I'll add to my question of "Just how long do you want?" - how much data do you want to store, and how often do you want updates?
The top search result are GitLab docs for pushing to or pulling from another repository for mirroring.
No it isn't. Just buy an external drive or something and copy your repos to it, done and done.