In my personal experience with self-hosting, don't do it to improve the availability. Because you can't really match a company with a high availability setup,

In my personal experience with self-hosting, don't do it to improve the availability. Because you can't really match a company with a high availability setup, with a 24/7 experienced on-duty team, and with a very strong incentives to have an up and running service. You may never have any issues but it's likely that your self-hosted system will fail as well, and not necessarily at a convenient time. Self-hosting is interesting though, so you should run your own vault server if you think you will enjoy maintaining it.