The n64 wouldn't heat THAT muck to burn it yet alone raise the temperature that much
But like I said, usually, the nintendo machines are well built. I mean I once watched a DYKG video and they had like crazy ambitions for the original DS being able to survive a high fall from the height of where your pocket would be. Oh, and once, a gameboy burned during a war and it was still functional
I also saw a 3ds partially melted, still works
The Wii from what I hear is VERY hard to overheat. Like, really hard, it doesn't surprise me much that the n64 can endure a 3 day of rendering without overheating.
And let me assure you, computers nowadays have a thing called thermal throttling. There's sensor near the CPU that if they detect a very dangerous temperature, the CPU would cool down by itself.....which results in worse performance and slow response time (like unusually slow). This is to prevent to burn your house down...so, I wouldn't expect the n64 being able to burn....you have to overheat it like very hard and quick