I am late to this thread and I haven't got beyond this post by Adair M .... so I might regret jumping in at this point .... but I must. This quote says everything about the subject so far:
So there's no purpose in being skittish about getting those root choppers to work. It isn't even a question of realizing it a few years later. By the next season from today you'll wish you'd done it now. Adair's words and picture are a great inspiration. Actually, I don't like the olive as bonsai, but seeing the photo of all the roots ...... hmmmmmm ..... I may have to rethink my opinion of the thing.