Scars in children can take up to two years to fully mature and yes topical mederma or other scar fade remedies work well. As far as timing of the scar is concerned, there is no right or wrong answer there. If it is clear that the scar needs to be surgically revised, then there is no benefit in waiting. However, if the scar is not depressed and not tethering a structure or involving the lip line, then my opinion would be wait at least two years for it to mature. In the interim, laser treatments are available to help a scar heal faster and better. If it is a nice straight line that is narrow, my recommendations would be to wait and let it fade out over time. I hope this information helps.