How long should i let them go under 400w hps?

i am trying to maximize my space, time and light.. so my question here is how big is too big for a 400w light? i have lst'd a bit and they are about 18 inches tall and very bushy. just 3 plants in 5 gallon smart pots.

what i am wondering is how far will the 400w light penetrate? i dont want to waste time vegging. any input would be great

i have pics which i am going to add to another thread
thanks

I would say strat flowering or continue to lst because the 400 will not penetrate that much if your plants are 2 feet already.
Or i guess you can add some cfls for the lower buds.

yea i have been lst'ing and supercropping trying to keep them the same height with a level canopy. i got them when they were almost a foot so they are not quite lst'd like i would like. i think i am going to take off a lot of the lower branches when i flower, im trying to get 8 main colas per plant and maybe take off all the other branches

Yes taking off the lower branches would do good since your 400 wont penetrate much below the canopy