I don't think you should try to increase your draw length just because you think you should, or because you think you need more energy for some reason. However, if you are drawing less than you should because of some problem with your basic form, such as dipping your head to the string rather than bringing the string to your head, that's another matter. I think trying to get longer just for the sake of getting longer can create problems of its own; it did for me, as I literally overdrew the bow and had no room left to expand, so all I could do was creep, which I did, consistently.