I'm one the few here that have it separate. It IS a little tedious, but honestly I don't feel comfortable posting fanart on what is supposed to be my comic's official twitter. When it comes down to it, fan work and original work draw two completely different audiences, and in my experience it can be a drawback if you're known for one but not the other.
I think it's a little different too because my comic is a team effort and we're trying to be seen as professional. I also wouldn't want my personal views meddling with the branding of my comic too much since it's not just a one woman show.