nobody getting back to you? sorry.

I'm no expert, but a lot depends on the size of your growing space. if it's small, you switch early. I have plenty of room and veg for 6-8 weeks. some say after they are 10" tall, but this gets confused if you're LST-ing the plant.

with the Sea Of Green method, you grow only small plants, switching to 12 hours or less of light when they are as short as 6".

basically, it's up to you and the size your grow space can accommodate.

hope that helps.