Ashley, If it makes you feel any better - I had a render tonight that took 9 hours. I'm not complaining about the length, pretty usual for my renders. But when I looked th the image this morning - all my ecos disappeared. The only few trees remaining where put there as objects.  As they were all painted, it is annoying -takes time and doesnt look as nice as I remember it :(
Cant tell if it was a v7comp bug or a 'me' bug. Although how I managed to clear the population of 3 ecos in one unintentional go, I have no idea. Sad either way.

"I paint that which comes from the imagination or from dreams, or from an unconscious drive. I photograph the things that I do not wish to paint, the things which already have an existence."
Man Ray, modernist painter
http://artpearl.redbubble.com/