We have a self-hosted Premium instance and have 30min of downtime _every day_ while the database is frozen and backed up. We've been told that it's a known issue being discussed with GitLab but that could just be CYA. But in any case, it's the "at scale, while changing" that tends to cause problems.
Perhaps this is a continuing argument for self-hosting, especially if you don't have to expose the instance publicly. But then, if that's an option, you can also self-host GitHub (though I have heard less anecdotes about the stability of that).
