I agree that orbs are parts of energy from life finished as we know it on earth, but I do not believe it has to do with passing on and not yet moving on. I say this because a year ago my 52 year old brother died from liver failure. I began "finding" orbs (which I'd previously known nothing about). Now, a year later, I not only continue to photograph them but they are everywhere around me and my home- fantastic images indoors, but even more intense and active in my front and back yard. It makes no sense to say that suddenly orbs are all over the place... since my brother was only one person...these lights are everywhere and never cease to amaze me :) I think they are simply representing many many lives lived on earth, and his death introduced me to them.
Also, after a year of having fun taking these pictures, I actually saw an orb dancing on my ceiling. Last night, after taking many pics of orbs in motion, I realized that just prior to taking each shot, I was SEEING the orb!! I saw its motion- very gentle but quick flying.