I think it's safe to say that you shouldn't do anything with them until you develop an exhaust leak. I don't like using high temp silicone on the gaskets. For one, it shouldn't be necessary, and 2 you have to take the header completely off to clean up the mess the next time you change the gasket. The best gasket I have seen so far is the factory replacement Fel-pro gaskets you get from the parts store. Here is a little trick for you. Each end of the gasket has a hook instead of a hole, so you can just drop it down over the end bolts. Instead of removing the bolts completely, just back them out until you can get about a 1/4" of gap between the header and the head. Then take the new gasket, and cut out the bolt holes straight down with a pair of dykes. Then you can rip the old gasket out, and drop the new gasket straight down onto the header bolts without ever having to take them all out and therefore have to struggle to line up all those individual flanges again.
Kurt