My old 5D II was the same way, I had two of the 5D II bodies and the older had gotten several hot pixels. But you were doing 30 second exposures here, and if you did several in a row I could see how it would push the camera to its limit. I don’t think it is anything to worry about yet.

But then maybe this is just something you noticed that was always there, and it is your subconscious setting you up with a reason to pre order the 5D III.