As long as you want. It is an exact replica of the plant it came from so you will know how much she will stretch in preflower as well as the exact amount of days until harvest. With a few runs of clones of a strain, you can really dial a strain in! It just keeps getting better and better as long as you take notes and change only one thing per run. The mother plants should give you a great amount of information to the amount of space they will fill when finished! I just did 2 tents with 16 in one that is gonna be flipped after only a couple weeks of veg but I am going to let the other 8 in a 4x8 veg 4-6 weeks before flipping. That way I will have my harvests spaced out far enough apart I won't be trimming all the time. Trimming is the worst process of growing for me!! I really don't like it! I am glad my finished product is only for me so I don't have to get it into dispensary quality condition before jarring it up. Have fun and happy growing my friend!!