veg time

I recently moved from the state of Oklahoma, and have grown out doors 14 years. I'm now in So Cal in the desert so the out door growing is not an option. I have purchased the proper equipment and spared no expence. I have built two rooms for the veg and flowering. Long story short, I have an nice set up with about 9 feet of vertical hight before I run out of room to raise my 3 1000wat HPS. I'm veging under 5 24" protatractor lights form DH.
My understanding is to stop veg growth when the plant has reached 1/3 of my vertical limit. My question is this, with my lack of experience indoors, how long should the veg stage take for the plants (Pur Kush from seed) to reach that hight? Although its less than 1/3 of my limit I was thinking 12" tall then going to 12-12.
Someone school me, please. Thanks in advance, Scott

Welcome want my ink.
With those lights and if ventilation is optimal I would say 45-60ds veg and you should be at 3ft from floor.

Now that is from seed.
If you have clones then that time will be shorter.

In your setup I would probably go for the largest pot from the get go.

Happy growing

I have Plenty of nevtalation. 10" blower, carbon filter, proper duct work for intake and out. I also have 5000 btu window ac unit set on a thermostat @ 78 in case all else fails. My distro box allows the ac and fans to run on there own circut. So the temp is well maintained.
Thanks so much for the input. Artificial light is not my strong piont (yet) so the time frame info helps alot when planning my next stage of plants. I also was fortunate enough to meet someone needing to move out of there house and I bought two mother plants to take clones from.
This indoor growing has brought me so much more in tune with my plants. It makes ya feel kinda like Father nature creating a ecosystem in doors is so much fun. Thanks again......Scott =