newbie question

OK, here's a basic question thatr shows my ignorance...

I know that during the flower stage when lighting is 12 on and 12 off you have to be careful about keeping things dark when lights are off but is that the same for the veg stage if using an 18-6 cycle? Will I stress the plannts or risk hermies if I have irregular lighting???

i wouldnt want "irregular lighting", keep things 18/6. However, u can go in everyone once in a while during the dark cycle for vegging without problems. You can even keep light on 24 hours if you want.