When should you move the plants from these little ...

I would say , as it gets harder for you to keep the res full but another good way to tell would be when you check your root system if its filling up a good portion of your bucket I would change the pots then too because it may give the same effect as being root bound . There's no real way for me to give a real answer unless i seen your root mass but based on what I'm seeing in the pictures your plants are big and healthy and likely have a bad ass root system , Never hurts to give them more room to expand and become more kick ass as a result your plants will become more robust and kick ass! I know Iam no master but i hope you have found this information useful on understanding when to change from the starter box . -Happy Growing!