Hi guys,
I do not understand why some ppl recommend lst instead of supercropping ?! lst helps multiplying branches; you lst your plant to help cover your mesh if you're scroging for example, and supercropping is to increase bud size and potency (talking about good supercropping here not snaping the branches completely-you can do that with some strains during flowering even at late stages), you can lst and supercrop your plant no problem at all as long as you don't do it at the same time which will stress your plant and stunt the growth.
there is a big difference between supercropping and lst, when you supercrop you actually increase nutrient and water uptake of the plant because it will double the size of the stem that you have slightly damaged by twisting or snaping it resulting in a bigger and more potent bud, lst will never give you the same bud size as supercrop but will help branching ( you can have multiple popcorn sized buds in an lst'd plant or just multiple regular size buds but that's it.
and in answer to the op question, you can supercrop usually untill 3 weeks after switching to 12/12 (this is what experts recommend) but lots of ppl don't understand how to supercrop properly, and usually they snap the stem completely making it hard for the plant to recover during flowering saying that, some ppl get amazing results with snapping stems but you should do it during veg or early flowering. it also depands on your plant abilty to recover (some strains recover fast some don't and may even die), also the environment is important, if you're flowering room is too humid for example them mold can attack your plant where u snapped it and you can have serious issues.
so as i says i don't get ppl recommending lst instead of supercroping !