I would say the main drawback to vegging longer, is the need for more light, as they get taller. If you're using a 400 HPS, for example, a plant that finishes much taller than 2', is wasted space, IMO, because the lower budsites won't really produce much useful smoke. Also, as the light becomes less effective, the plants stretch more, making them more prone to falling over under the weight of the buds. Sometimes that's a good problem, but other times it can be a real pain in the ass.lol An exception to the rule, is if you veg longer, and train the plant, to keep the heigth controlled. If you use that etra veg time to make the plant wider and bushier, rather than taller, the extra time is a good thing.
