Unless you have a vertical setup or are doing some training, it usually doesn't make sense to go past 4 weeks in veg. I found this out on my most recent grow. They got to about 3 and a half feet tall, but the usable bud would have been close to the same because you're getting similar light penetration either way. I probably got some extra popcorn nugs out of it, which wasn't worth the extra 3 weeks I gave them in veg.