and without knowing dimensions of your gorw, or even your lighting, noone can really tell you how long to veg for. You need to consider the capabilities of your light, and that the plants will double to tripple in size once flowering.
Depends on Your grow Room restrictions Height, and Sqr. Feet.
How many watts is your Light? The Bigger the Light the Bigger the plant can be.
How many Lumens per sqr. Foot?
"The More Light the Better" as long as you can control temps.