Rainey,
This is not a major problem. I know you think otherwise at the moment, but ...
First of all, and as you've seen, it's only occurring with longer exposures. Thus it seems as though it may be heat related.
It may be that you can map the sensor in the camera's firmware; I'm not sure. I think we can do this in the Nikon's; I don't know about the Canon.
But importantly, it's only happening to one or two specific pixels. It's more an issue when you pixel peep, which is something that we all tend to do. The reality is that, when you're printing an image, you don't normally get to print at an individual pixel level, and thus the problem is masked.
Unless you're printing super large prints, you will never see the problem in any printed image, nor will this issue manifest itself in any real practical sense.