Ok, we’re talking about 2 different things: the overheating is due to the sensor being exposed, so it can capture the image. It doesn’t matter where you record it, be the card or via the hdmi – the sensor will get hot, there’s no turnaround, BUT… id doesn’t get hot so fast. As Darrell said above, you can shoot for hours, turning it off frequently, with no problem.
The other thing is the 12 minutes limit, for recording on card. The simplest way to avoid it, is to stop recording, for just a second, say before 10 minutes, maybe when asking a question.