Not sure if its already posted but.
Was watching "Corridor Crew" and they made a Youtube vid about this. Just like them, i always had the impression, that in real life the Pred would still see Aronld because of the Mud being Heated up by Arnolds body heat. Anyhow i was very surprised by this recent youtube clip. :)
I remember that this was tested on Mythbusters a long time ago. Though they generally are sloppy with how they test stuff, but I believed cause of the test that this would not work. And yes this is limited, but it's much easier to do and lasts much longer than I thought. Wow, I'm so glad I saw this! Who would've thought that Predator actually had potentially accurate solutions to the thermal vision.