How long you veg depends on several factors. I've heard that the longer the veg, the bigger the yield. It's a safe bet to veg until you see preflowers and that way you'll know your plant is mature. Also, where you're using cfls their growth will go a bit slower than if you were using HID's so, the longer the better. If you don't have a lot of space that's a consideration too because your plants will double in size during their flowering period. You'll just have to wait out the veg stage to see how your plants progress. Happy Growing and Peace!