It's been like 3 months for me that I am trading with a demo account. I believe that there is not a limit that you can say that now you can close your demo account and do a full time live trading. Demo accounts are always helpful for traders to practice or implement new trading strategies. So If you feel like you have given considerate time in the demo, now you can begin with a live account as well. A demo account is always handy for keeping the learning process going on.