Veg vs. Flowering

I'm wondering...how long should I veg my plants for? In my state for medical I'm allowed 6 plants, 3 mature and 3 immature, but I'm going to be growing them at different stages, so I have a perpectual garden. But how long do you let your plants veg?

I have a 600 watt HID set 370 watts with a sodium bulb, and another 400 watt HID set at 400 watt with xtra lumen control hanging right night to it about 36 inches from the plants. I don't have an inline fan hooked up yet to the lights, hence why their so far away from the plants...it's hard to get around for me with my condition, so I ask my friends for help, and of course their to busy, but when it comes to smoking some very fine weed, they can't get over to my place fast enough.

Well, to get back on topic, I have one plant I've been vegging for about 2 months, and it's about 2 ft high and very dense, so I'm guessing it's an indica, so when should I flower it? I've read that an older a plant is, the more cannaboids it has, (I've heard that's why a lot of places will clone the strain to increase the CBN in it). This is only my second grow, and I'm looking for quality, not quantity...is there anything I can improve upon?