Does anyone know what the life expectancy is of a video card?

I've had my computer about 2 years now. About a year ago, the computer started shutting off on its own. The screen would first shut off with the message "No Signal" popping up. Then the computer would power down. I took it to a friend and he said the vid card was bad. He put in a 'really nice one' (i'm not at home since I don't know the exact name of it right now). He also reformatted it for me. Comp worked fine for about a year. Just recently, I stopped using the computer for a month or so because I just got so busy in life. I went to use it the other day. I turn the comp on and almost immediately, the screen pops off with the same message, "No Signal" then the computer powers down. This happens every time I try to start the comp up. I've checked all the cables, cords. Everything is hooked in. Surge works, outlet good, etc. Does anyone have an idea of what could be wrong? Is it the video card again? Is it common for them not to last long? Could it be the motherboard? Any advice I would appreciate. Thanks!