It doesn't have so much instability because it doesn't have users. That is not the fault of SR, but a limitation of how much Tor can scale. If SR wants to fix this issue one thing they can do is use two different .onion domains that point to the same thing. When one becomes overloaded the other will still work. That is what Freenode did once they couldn't scale with the amount of users using their IRC server over the hidden service anymore.