It depends on what you want to do with your blog. Are you just writing for the heck of it? Do you want to make money with your blog? Are you using it to share ideas with others?
I tried a blog last year for about a year, writing about new electronic gadgets, and I have a hard time sustaining my writing....meaning that I just could not keep up. I wanted to earn some money, but found that if you want traffic on your site, you need to spend a lot of time on it, not just advertising your site, but also constantly putting new information on it. Since the electronics industry moves so quickly, I just couldn't keep up (just didn't have the time to constantly write new things). That's just my experience. Again, it will depend on your PURPOSE in starting a blog.