well... You can veg for however long you want. 6 wks would be minimum. If you have enough light, the bigger you grow your plants, the bigger your return will be. If your working indoors, than 8-10 weeks of vegging is probably the max. The general flowering time for plants is 8 weeks after being placed in 12/12. Another common time is 10 weeks. Some plants have up to 12 or 16 weeks. On 8 week flowering strains, usually they have all of their girth by 6 weeks, but they need that additional time on the plant to ripen and fill their crystals with THC. Once the crystals are mainly white, with a few being clear and another few being amber colored, they're ready (buy a microscope). Even if a plant is listed as an 8 weeks strain, thats sort of a general time. I just harvested 5 Aurora Indicas. They are listed as 8 week bloomers. one of them was finished at 7 weeks. two were finished at 8 weeks. two were finished at 9 weeks. None of them were ready at 6 weeks. This is all after lights are switched to 12/12, not after flowers start appearing. Flowers start appearing at 1.5-2 weeks.