There are all these "lol we blocked you for abuse, good luck doing anything :^) I guess complain on twitter lol" horror stories that I don't want to be locked down to one provider that does _everything_, the way Google or Apple does.
Even the fact that I have all e-mail at Google that can randomly ban me for "abuse" makes me scared, but I don't want to figure out how to move all my mail history to ProtonMail or AOL or whatever. I will need to have that as a risk.
For me, I find the Keychain to be too chaotic. I use 1Password.
If you’re an Apple house, it’s a great solution.
1. I do not use the MFA capability of Keychain at all. Putting your MFA, username and password in the same store is fucking stupid. I have a hardware TOTP token. Backup codes for that are however kept in Keepass.
2. I keep an offline backup of everything. Never trust a cloud backup!
3. All vendors are ephemeral, regardless of their size. Everything I have I have a carefully planned exit plan for.
As other people have pointed out, your keychain is on disk, but if you lose the Mac and find out your MFA codes don't work or something (this does happen) then you're SOL. Keep a backup.
I just had my keychain corrupt last night while I was testing the SecItemAdd API. So keep that in mind, maybe make backups. I was pretty shocked that you can corrupt the keychain using just the API, the entire security process started to lock up too. I had to (manually!) delete the entire keystone and start from scratch. Luckily I don't rely on it much.
It is worth noting that after you back it up to a remote location, it may not be a very secure concept anymore.