Another issue that is related to a blinking heated seat switch, in reference to 06 models, is that one of the vent doors did not register correctly. When you start the truck, the HVAC will occasionally go through a system check to make sure all the blend doors cycle correctly. If one of them is having a problem the heated seat light will flash until it cycles again, or after power has been disconnected, and everything is OK. If not, a blinking light will continue.
You can force a cycle check by disconnecting the battery for a few minutes. It should go through a quick blinking cycle, for about a minute, then go to a slower cycle afterwards, if something is wrong.