Veg time for sativa grow

I am currently vegging strawberry haze, ultra haze and purple lady. how high should i let these get before flowering? There is 7' of room but need to minus about 2' for the light etc...

I say 1 ft.

I have two super silver haze and one blueberry plant currently growing. The super silver haze just hit 13 inches and the blueberry 7 inches today. I figured today was the perfect time for them to be put in the 12/12 flower cycle. If i wait much longer then my 150W HPS light wont be able to make the bud grow as well as i would like

probably 18"

6 nodes and they're mature. That was around 8" for me, then when it hit 4 feet I tied it over and the side branches came up. Tie it over and then it grows a but more and you tie that over.
The other thing you can do to LST. I'm doing that in my current grow and they are much shorter and bushier so far. i just took pics (in my sig below) of the lil one in flower, they are widening and getting bushier. You can also see the big one tied over which has 4 weeks to go.
Hope thats helpful

would it benifeit to top one they hit 6 nodes then?