I was helping another person in the Windows newsgroup who was complaining that their laptop’s screen goes blank after 30-60 minutes and they have to open and close the lid and press the power button to get it back. My advice:
It could be caused by overheating, dust, or maybe a loose connection. Try holding the laptop up, with the display’s screen facing the ground. Gently shake it a bit and see if the screen goes blank. If it does, then that’s your problem; it’s not a laptop, it’s an Etch-a-Sketch.