Can any Android device be set to not auto power-off? If I buy any no-name Android tablet from ebay etc, is there a chance it will not allow me to force it to stay on all the time?  In other words, is "never auto sleep" a universal feature of any android device?

If not, how can I tell?
Check out the free StayAwake app


  Simple app to toggle a stay awake mode.
  
  enables stay awake,
  
  
  always
  if plugged in to AC/USB