I'm glad I'm not the only person that thought this, because I'm a HPC batch admin and that sort of machine packing is just what I do.

I'm glad they found a solution which seems to work out really well for their use case. Changing the algorithm to use the machine for an hour would imply that some tests may wait to be run, and that could be a bad thing for TestingBot (I'm not sure what their SLA is).

Going to their own "cloud" though will require them to either overbuy capacity or eventually make a push to increase utilization, so they may end up making that algo anyhow.