First of all good post... i've seen a lot of people who miss this aspect and come asking why there plants have a stunted growth (Then as u pick up the pot u feel the inbalanced weight between the top of the pot and the bottom)

To add some information if wanted:
Symptoms that the plant needs a transplant: Plants that have roots that are being limited from a small pot normally have a small amount of branches and overly strech upwards.

After a transplant (which is the second most traumatic experience for a plant. the first being the clonation) the photosintesis and the production of cloraphil is slowed, therefore it is recommended to transplant at the last hours of the day. That way the plant can recover at night. Also the transplanted plants should have a softer light for 2 days, therefore the leaves can grow at the same rithym that the roots can contribute water and nutrients.

Tranplanted plants require low levels of nitrogen and potasium, while needing higher levels of phosphorus. Any product that contains Trichoderma fungi or vitamin B1 will help to reduce the shock of the transplant. Obviously is if the transplant is done correctly, textbook, then there won't be signs of stress.

In jorge Cervanes there is a table that u can use to know when to transplant. Here it is:
2-6 weeks pot of 10 cm
6-8 weeks pot of 7,5 Liters
6-8 weeks pot of 11 Liters
2-3 months pot of 19 L
6-18 months pot of 38 L


(important note: as stinkyattick said, it depends on ur situation and very important is the strain) Also if you use "Spin-out" the plant can stay in a smaller pot longer.

Question for stinkyattic: Why do u wait for the soil to be alil dry before doing the transplant? any particular reason?