Note that we do have onboard monitoring for temperature, voltage, and current, with thresholds set to shut down the board if it appears to be entering a situation that would cause damage.  We provide a utility (console and GUI versions) that you can use to talk to this onboard controller via the USB and see what is going on with all the sensors.  Unlike GPUs and CPUs, FPGAs have no inherent thermal throttling, unless the FPGA developer builds that into their logic, which is very rarely done.  FPGAs also burn more power as they get hotter, so from a power efficiency point of view, it is better to keep them cool.