Demo accounts are a waste of time. You are much better off putting 300 dollars in a mini account and getting real money experience from the start.
Ask anybody and they will tell you that their great "system" and great discipline seemed to go out the window when they first went "live". I am not smart enough to know why, but I do know that things are just different when real money is on the line. I am not talking about quote rates and disconnects, I'm talking about actual trading.
No matter how seriously you undertake the demo experience, you will find things are not the same in live market. Some demos allow the user to define how much money to start with, this is nice but does get at the heart of trading psychology. 5,000 demo account still not the same as 5,000 real. It is closer to what most would open a real account with though.