There are downsides of low temperature and low speeds that a fan can help avoid. Low temperatures can lead to problems with bonding between layers and low speeds are just too slow! I also find it to be a struggle to hit my low temperature target without undershooting ... and when you are printing that low of a temperature that can lead to a bad layer or a nozzle jam. This is even though I use Simplify 3D and hit my target temperature by lowering a degree a layer.
I think that I can adjust my fan modification to replicate the quality of the center Marvin and still avoid the fate of the Marvin in front. It is all a balancing act that requires extreme levels of patience though!