I've written a good deal of my two current comics, but they're still pretty early on in terms of actually being produced and finished. My sci-fi/mystery story Atonement just published page 12 and my horror/gothic fantasy book I, Necromancer just published page 10. The one advantage to producing and releasing the pages so slowly is that I feel pretty confident in making big improvements to my approach to writing/editing them already. I feel like going the route of releasing them on the web first has definitely helped me learn, and man, that's pretty cool!
Good luck on Caster! The banner is a really great start if it's any indication of the art style within. There are a lot of great threads on this forum and articles on the newly launched StArt Faire magazine on writing comics (full disclosure: I'm one of the magazine contributors there) that might help you break through any blocks you get. I'm primarily a writer myself, so I understand how challenging long-form writing can be.
I definitely forward to reading your stuff once it's released! : )