I was having problems running ~8 hour prints via pronterface - printer would just stop moving at a random point several hours in and stay hot. Pronterface showed a random "k" in the terminal. Research showed this problem is related to the ramps board getting too hot and disrupting serial communication. I have solved this with a ramps fan. The stepper driver heat sinks were hot to the touch and now with a 40mm fan on a quick and dirty mount they run cool to the touch. I recommend running a ramps fan of some type. Due to my wiring runs, I couldn't use the four legged mounts that have the fan facing the board. I had to do a mount off to one side.