I suggest designating one or two mother plants for your grow opperation. I have 3 mother plants that are almost 2 years old, when my mother plants start to get to old I just pick the strongest clones to take their place. I think that growing with cloned plants is the easiest and most efficient method to have a constant supply of weed. As far as cloning from a clone you could do it indefinately as long as you keep the plants healthy.