The seedling stage can last between one to three weeks. At the end of the seedling stage your plant will have between four and eight new leaves while some of the original bottom leaves and cotyledons (leaf of an embryo of a seed) may have dropped off. In rockwood, that would be once you see roots making thier way out of the bottom of the cube. 2 or 3 inches is cool also from what I understand... Good luck to you Bro....