I expected a mod or admin to tackle this. But as it has been a little while, I will take a stab at it.
Lots of us read just the new posts in the thread. When it comes up, we click on the button that takes us to the first unread post, and read on. We sometimes don't realize that the problem or situation is long over. Sometimes we say how sorry we are that so&so lost their dog. Or, we might tell someone to get off the internet and get to the vet NOW, only to find out that the dog in question was treated two years ago.
Lots of times the OP has been long gone, and here we are discussing it as though she is going to come back and use the information. Sometimes the threads are still informative, but more often, people will say, "this thread is old." They will close it.
If the thread is about a specific situation, it really isn't fair to resurrect it and talk about it, when the people/dogs in question are not aware that it is being discussed.
And if you are just bumping a thread -- typing "bump" so it comes into the active list again, then there really isn't new information. If you want to discuss cow hocks or megaE or something, probably better to start a new thread, as it is a whole different group of people that may be responding.
Bear Cub, Hepsi-Pepsi
Cujo2, Karma Chameleon
Ramona the Pest, Kojak -- who loves you baby?
Tiny Tinnie, Susie's Uzzi, Kaiah -- The Baby Monster.