[RC-Monster Mike]

Generally, voltage/amperage spikes are controller killers. Usually, failures don't happen from heat buildup (controllers are thermally protected), but from wiring issues or bad connections. A long set of wires connected to a lot of cells is a recipe for controller death. I have had Schultze controllers go before I even had the car on the ground and they blamed the motor connectors (BS if you ask me). Keep the wires short and make sure the solder joints are quality. This as well as selecting the right controller for the job will lead to a long controller life. A fan never hurts (I always run fans on my controllers).