When should I switch from closed hole flute to open holed?

I have been playing for about 3 years, but that doesn't stop me from succeeding. I am the youngest player in my band and I have tried honor band in which all the older people didn't get in. I was the only one in the school to get in honor band. I play piccolo, I am good at tuning, great vibrato, fastest fingers in the flute section. Also if it helps, my closed hole flutes have little circly dents (but not horrible dents) just a little dip thats circle where the holes would be in. I play an armstrong.