There’s no one-size-fits-all answer. If you wait too long to rotate keys, compromised keys can be used to gain unauthorized access and have ample time to wreak havoc. If you rotate keys too often, you’ll end up with a significant manual burden.
It’s recommended to [rotate keys as often as possible](/blog/rotate-ssh-keys/) while considering the difficulties that can arise, or you can use Tailscale to make this process simple.