As I see it, the nesting effect is the ivory tower's answer to the parental variant: one finds oneself a bit nostalgic for the old days when one first started working with a student, and a bit apprehensive (as the pupil must also be) as well as hopeful about the future. Like parents of multiple children, one often looks to the younger "siblings" for something to busy one's mind with (well, more so than usual). And, as with Papa or Mama Bird toasting - er, tossing - their fledglings from the familial nest, the advisor sometimes has to curb the tendency to keep hovering and giving advice. It's an interesting effect - I wonder if any psychologists have studied it. (I'd be surprised if no one has; after all, in academia, we have an incentive for getting more of these particular human subjects!)
Dr. Michael Loui, another Illinois professor, wrote a talk titled "How to Choose A Thesis Advisor" that I read about a year before I graduated. It's good advice, and though I was able to find an excellent advisor (Dr. Sylvian Ray - recently Professor Emeritus; sorry, dear reader!) without benefit of it, I think new grad students should all read it. Dr. Loui writes: "... although you start as an apprentice, ideally, you should end as a colleague". Words for the novitiate Ph.D. advisor to heed as well.