I used to play my games for nearly two days straight without stopping when I was little and never once did I burn out a system. I did fry my original Gameboy once but that was because I tried to use an AC adaptor meant for a CD player. The back of my Gameboy started smoking and I heard this sizzling sound and that was the end of it.
3DS Friend code 4038-6006-7917
Wii Friend code 3553-5293-8702-0039
Smash Bros. Brawl 0001-3032-2653
Mario vs DK: Minis March Again 3310-6435-2823
Wii and 3DS ID Link