Some people get all worked up about smoking the cavities and how it's not needed, but I do it on most of my molds too. It just makes casting easier, with no ill effects that I've ever seen.
To be honest I rarely preheat my molds much other than dipping the end in the pot for a few seconds, but usually get good bullets on the first cast with smoked cavities. Once a mold is broken in though and used for a while, I usually don't need to go back and smoke it again.
