I've heard of people having mothers alive for years. I think what triggers the change in the plant where it decides it needs to hurry up and end its life cycle is the change of lighting. Certain ammounts of darkness cause hormones in the plant to change it to flowering mode, something like that. I know some annuals, like common garden stuff, have a lifespan determined by time, and putting them under 24/0 lighting won't cause them to "stay in veg", but with cannabis it needs that lighting change to undergo it's final flowering phase of its life.