I personally believe sim trading should be used only for an extremely short period (say, 100 hours of training, tops).
You should get some skin in the game as soon as you know how to operate a DOM. Mind you, it should be minimal skin. No futures. Use spot forex at 10 cents a pip, for example. But get some real life emotion and real money in the process. Each bad trade may cost you $1-5 for example, a cup of coffee.
Those who stay on sim for months are not practicing to become traders. They are practicing to become sim experts.