As discussed previously on these forums, that is a perfectly safe operating temperature for the CPU as they are designed to run that hot. Although if you are like me and would rather be on the safe side, buy a USB fan and attach it to the router (Or an external USB hub connected to a power-point for multiple connections). This should decrease temperatures nicely, my AC68U is running around 60 degrees after wiring an old CPU fan to a old microusb cord. Very cheap to also buy off eBay if you want to save yourself the trouble.