It isn't a simple, cut and dry issue. Other things to consider is that a typical VFT purchased form a nursery, whether it be a locally owned greenhouse or Lowes or Home Depot has purchsed a batch of plants fresh out of tissue culture and those plants seem to be healthy enough to commence flowering. However, most of these places do not how to take care of them. They water them with tap water. They don't know about open tray method. They leave the top on all the time or leave it off. They err by giving it too much humidity or too little. The plants receive indirect light. In short, whatever fine shape the plants were in, upon arrival, they have been since under increasing stress every day they reside there. Then a customer buys one and usually they have similar lack of knowledge as the retailer and thus perpetuates the stressful conditions. The customer tkaes thae plant and puts it on a window sill, so it receives filtered light and thus receives less solar energy. By the time the plant actually flowers so many variables have gone against it that the stressors have out the plant over the edge. It is the proverbial "straw that breaks the camel's back." The plant dies. Your best bet is to not let the plant flower when you frist purchase it, but follow the cues that nature provides. If purchased in the spring, put it outside. Let it grow but don't let it flower. As fall approaches let it get less light and lower temps. Have it go through a good three month dormancy. Gradually increase light and temperature. Get it outside again, depending where you live and whether it will freeze. Bottom line: give it dormancy and give it as much sunlight as possible, along with balancing humidity and air circulation and de - whatever water.