The following links are a good source of how and when to re-pot your bonsai trees. Please keep in mind that the proper time to re-pot a Bonsai depends on where in the country you live. It is always best to contact your local Bonsai club for advice on the proper time to re-pot your trees.
Apple Tree Bonsai, April 2015 by Nigel Saunders
Bill Valavanis: Repotting Begins! This is a great article by Bill on how when and what to do when re-potting a Bonsai.
Fall Repotting by Brent Wison
Graham’s Guide to Repotting Bonsai by Graham Potter New 11-1-2016 Great in-depth article on the importance of re-potting!!
How to Repot Bonsai Trees – The Basics Video by Graham Potter
Literati Prunus Spinosa ‘Fifty’ final potting from Duffet to Albright by Tony Tickle New 10/07/2016
Repotting a Beast! (Japanese Black Pine) by Peter Tea
“Repotting” a Rock Planting by John Geanange
Scots Pine Yamadori Goes Into It’s First Pot by Graham Potter New 12-05-2016