Well, any use of an electronic is most likely going to increase the chance of it malfunctioning. The more you use something the more likely you are to encounter problems. I'd say that's the case for most man made things. The more you drive your car the more likely you are to have problems. The more you use your game consoles, the more likely they are to experience something like the RRoD. In fact, getting hot is exactly what caused the RRoD on the 360. If I recall, poor ventilation caused overheating, which warped some internal components, or, somehow messed with their contact with the mobo. Something like that.
I'd say Moscow is right though. I would hope in there QA that they did lots of testing with running video, and, would have recognized any problems already and fixed them. But, who knows.
I also have an X2, and, I use my phone daily to watch media. I have used it for several hours at a time, I'm gonna say I've done at least six hours before, and, never had any problems with rebooting or anything. And, I use my phone heavily all day long to browse the internet, email, social media, etc. and never have any issues.
If any of this does cause problems I would hope that it would fall under manufacturer's warranty.
As for the screen, I can't foresee any issues, maybe burnt out or stuck pixels. Think about how much use your TV gets.
If the X2 is built properly, it should last you for more than two years. And, I think it is. But, then again, I thought my 360 was too, and, bam, RRoD in two years.