An extra few weeks of Veg time, whether used to mainline, manifold, scrog or other...the reason for it is much higher yields than not doing the training.
I averaged over 200g per plant in my first grow doing this. 23 weeks total growing time.
Cannabis sites that teach these methods suggest a 30 to 50% increase in yield...based upon most grows i see these methods actually produce 200 to 300% of most growers outputs.