- last post: 01.01.0001 12:00 AM PDT
Well the forerunners probably did colonize the rings. They were probably used sort of like galactic hubs where they were able to live, and live comfortably I might add, as well as study and contain the flood. The large gas giant planets were too inhospitable and unstable to be able to maintain long-term resarch facilites, which is eveident in Halo 2. The constant violent storms on the gas giant presented an unsafe, and therefore unsuitable environment to conduct the long-term studies on the flood which were necessary to maintain the flood.
In fact, the forerunner seem to be very similar to humanity in this manner. We also portray our desire to create seemingly useless monuments as a testament to our intelligence and technology. Maybe the forerunner created the rings to be the ultimate combination of form and function.
One probable reason that the flood were able to surivive for so long is because they were being held in stasis on the rings as well as the research facilities on the gas giants, until they were accidentally released by the covenant. Plus, if not for any other reason, they're relatively easy to find.