Would have to agree from experience I demo trading too long, and in the long run it really dampen my trading until I just quit demo trading then I was better off. Demo trading is only good to learn the platform not to try to see it you can make profit; because when it's cash on the line either you know it, or you don't. Trading is forever learning
I totally disagree with the theory that demo trading is a waste of time or priceless. Demo trading is the opening bell for the new comers to gain some basic practices about the market. It has some drawbacks for sure but you have to overcome them in order to trade live account with the probability of long stay.