I want to grow longer. Need some advice please

Growing a plant now, it started to pre-flower a few pistils here and there i can clearly see. My question can I continue vegging her for longer. Shes on 18/6 right now. Do I need to switch to 24 hrs and keep the light on her?

...as long as you give them long days of light (18-24 hours) they will stay in a veg state....this is how you keep mother plants.