There is no time limit for practicing using demo account. It depends on each trader need. One thing for sure that without learning and practicing first, you won't be able to generate constant profit. If you fail to earn constant profit, then forex is not the quick way to make money, but the quick way to lose money. So, take your time to learn it first with patience and focus before you trade for real money. Prepare everything first, then you could get what you aim.