How often do you increase pot size on growing material?

I have some smaller trees that I want to grow out in nursery pots, rather than in the ground. However, I understand that over potting can be counter productive to the growth of a tree. I was wondering if you guys have a standard for when you move developing tree into a larger pot to allow for more growth.

I use colanders or pond baskets, as they produce a better and finer root system in addition to promoting fast growth. I repot my trainer trees once every 6-7 years. After they are ready (between 10 and 15 years) I pot them in roomy training pots and then it is ever smaller with each repot.

I use grow boxes with mesh bottoms and tend to move them up every 2 - 4 years. I probably don't get as much trunk growth as some, but I get more chances to prune and adjust the roots. I am slowly moving to longer times between repots as my soil mix evolves to support longer times between repots.