Since you're looking to collect anecdata, I've had 100% uptime from my self-hosted GitLab instance, which has been online for about a year. GitHub may be on par with that, but it's hard to beat 100%.
I self host my gitlab and when there's an update it goes down for several minutes (well actually I don't know if it's unusable, haven't tried, but with the backup and the updates, it's long)
I'm the only one working on it, so that's not a problem for me.
I must have transposed "unexpected" downtime in my head. Yes, I update the box and installation periodically, and yeah, that is time that my GitLab environment is not available, so I guess it's not 100%, but like you I am the only person using it, so it's effectively 100%
I self host my gitlab and when there's an update it goes down for several minutes (well actually I don't know if it's unusable, haven't tried, but with the backup and the updates, it's long)
I'm the only one working on it, so that's not a problem for me.
Still, it takes time.