Was wondering what the limits are on this service - turns out they quite sensibly restrict the number of shells allowed per source IP address. This script shows it starts refusing new SSH sessions after a few connections back to itself:
Eventually starts showing this in response:
Also their Tor hidden service currently seems to be inaccessible. Perhaps there's a hard limit on the number of connections via that route, given that one can't restrict per any individual source due to the design of Tor.