Keep all 12 CFL's on during grow?? or 6x6500k veg, 6x2700k flower??

Should I keep all of my lights on even if they are for different parts of growth for maximum light, or should I use the right wavelengths for the right periods of growth even though that's less overall light? I'm thinking all but i just want to make sure.

plants recieve both red and blue spectrum both parts of the year and they have evolved to take advantage of that fact by having 2 types of chlorophyll, one that interacts mostly with the red side and one mostly with the blue side. using only 1 spectrum wastes that so its best to go with a mixed spectrum in both stages of the plants life. so yeah, all would for sure be the best way of the 2 options you listed..

have you considered 8 blue 4 red for veg and 8 red and 4 blue for flower?
the first will keep the stretch low and node density high, the second will give all the red spectrum needed plus some blue to contain stretch and enrich the overall spectrum.