its not an easy thing to harvest a plant and then let it veg again and then flower...
after you flower you have to set up the light cycle in veg mode for like another month, so it recovers must of the leafes and stuff, then again in flower mode... I belive you can harvest your plant only twice... but im not sure, and for what ive seen... this worked for a friend of mine but it was really hard eh... but anyway experience is the best teacher