Is this about watt efficiency? When they are small too much light forces too much transpiration. When they are teenagers, they will love more light as they will have the growth to support the transpiration.
I had a slight lockout of Phosphorus in my current grow at the cutting stage from just a 800 watt equivalent LED on Blue. I pulled it back 2 extra feet and they flourished.
If you do not care about watts and cost, then I would add it when there is good branching a couple weeks into veg. Peace.