Quote - That sounds like you're disk-thrashing, if Firefly is close to its 3GB limit. I don't bother letting renders finish when there is swapping happening, because the time you're spending now is not for quality.

That's certainly possible, given I've only got 2GB in this machine, but the times I checked there didn't seem to be a hideous load of page-swapping happening. This was a scene that took about three hours to render without any indirect light, so it took about eighty times as long with IDL. I was using one light, indirectly lit, with:
RT Bounces: 3 (needed to get refraction looking right, I think?)
Irradiance (AO) Cache: 0
Irradiance (AO) Sample Size: 10
Intensity: 1.0
IDL Bounces: 3
IDL Samples: 985
Irradiance (IDL) Cache: 25.0
HSV Exponential: 2.2