Sandstorm's hosting service (Oasis) is hosted on a service arguably/probably more reliable than GitHub... Google Compute Engine.
The big difference between Sandstorm and say... GitHub hosting (if the code is written for their APIs), is no matter whether I self-host or use Oasis, I can easily move my data to a different storage medium later.
Well... I am not going to claim that Oasis itself has better uptime than Github. :)
(Although we have had very few unexpected issues, we still need to take Oasis down briefly during updates. This is something I'm working on fixing, and until then I try my best to schedule updates when people are asleep...)
As to GP's concern about longevity of the service, the key point is that unlike any SaaS service, you can easily move your data off Oasis onto a self-hosted server running only open source software, and end up with exactly the same user experience you had before.
It doesn't really work for me because then I'd be hosting it myself. Even with Digital Ocean, I ended up shutting down a hobby website after a year because I was the only one using it (and then rarely) and I didn't want to pay the monthly fee anymore. App Engine would have been a better choice - everything I put there is still running.
Sandstorm on Digital Ocean might be somewhat better since I could cram more onto one instance, provided I was running multiple things there that I actually used.
The big difference between Sandstorm and say... GitHub hosting (if the code is written for their APIs), is no matter whether I self-host or use Oasis, I can easily move my data to a different storage medium later.