If a child have g6pd, is this for lifetime?

Yes: It's a forever condition but symptoms are usually quite mild. Most patients don't even know they have it. It's found when being worked up for something else. The triggers for disease complications are usually easily avoided.

G6PD: This disorder is considered a genetic disease and not curable, but controllable. Here is a resource for you: http://www.g6pd.org/g6pddeficiency.aspx