You have several old blogs that you haven't updated in ages. Do you think you'll ever return to any of them? How do you decide when it's time to move on to a new site?The dynamic here is actually a bit different from what the question implies. With one exception, these aren't blogs where I used to post before I decided to move on; they're blogs created to handle alternate writing projects, most of which I hope to get back to "one of these days".
The lone exception is the BorderTown blog, which was originally created in an attempt to find a replacement for a message board devoted to the Bordertown books. I'd forgotten it even existed until Blogger contacted me a couple of years back and asked me to claim it. So that one really is a sort of historical artifact.
The Shining Walls was a writing project - an attempt to see if I could finish a fantasy novel if I wrote it in blog-post-sized bites. It's one I'd like to come back to, but there are some issues with the plot and setting that I need to work out first. It's about a vampire who gets reawakened to help defend the last human citadels against the hordes of darkness that have overrun everything else. Scripture's Shadow is similar; it was going to be a retelling of the Bible, probably from the perspective of Cain, but instead the stories that are there are a lot more scattershot. Monstrosities was another such projects, which would have been (and maybe someday will be) a modern dark fantasy/horror story, or possibly short story collection. (I had another one for my All The Apocalypses story, but it seems to have gone away - probably from disuse.)
Right Behind isn't really mine; it's a group blog that I'm part of. It grew out of the commentariat over at Slacktivist, and our attempts to write alternate, better versions of the Left Behind books. It's been a long time since I've posted anything there, though.
Surreal Situations is my webcomic, and the only blog besides this one that gets updated regularly. It's an alternate-worlds-spanning pulp adventure, created largely from my children's toys.
So that's pretty much the whys and wherefores of my Vast Collection Of Blogs.