At the moment, I have a central blog with all of my interests (basically, its just all about the web and stuff). I would make another blog but I don't see a point if I don't monetize it or put any extra effort in maintaining another blog.
My blog is more or less nicheless, but having said that, I have a schedule to keep it all organized. Monday and Wednesday I write articles that can be about anything on my mind, anything at all. I've wrote about love, hate, pain, those people that need to leave my life, racism, spousal abuse, writing tips.... The list goes on. On Friday I put out a poetry post, and on Saturday I write a Serial Web Fiction Story.
The main thread that ties it all together is I make sure each thing I post is something I deeply care about, and I write it with quality and passion.
I just checked out your blog. Love that you have a schedule. I'm finding that more and more bloggers are doing that to ensure that their blog is kept fresh and current. Your blog, while it might be 'nicheless' has a great fluidity to it. It's a web of thoughts and images, and I like that :)
I have just one blog. I try to keep it updated a few times a week. I write about my life's observances and adventures living in NYC. It crosses several subjects such as life/lifestyle, health, food, cocktails, fun, etc.
If I had to do this over multiple blogs I would go crazy!
I write to inform and entertain, so my subject matter can be anything. I don't see the point of writing about only one subject, although I do write quite a lot about life in Hong Kong, Chinese culture and science. I also use quite a lot of original photography.