I wouldnt over-think it. Its ready to flower whenever you are. That's really always the case. If you flip a plant to 12/12 early on, it will keep growing until its ready to flower itself. You can start flowering 2 weeks in, no worries, you'll just have a small plant, but thats fine too. Preflowers are a good sign a plant is mature enough to start flowering promptly. Variables to consider are your height allowance, the yeild you want, and if there is a certain date you might need it done, but really thats all there is to it. There is no right or wrong answer.
Nice looking plant.