I actually write sci-fi as a hobby simply because it's so much fun writing and building the story, the charecters, the scenery, etc. The one I'm working on right now (as mentioned above) is called "Survival of the Lost Fleet" (I've posted up through chapter 32 in my writing section on my website linked in my sig if you want to read it) and is like 160k words at last headcount. Heck, I've got like 12 pages of notes which include something like 60+ unique charecters. I expect to have at least 60 more unique charecters as I continue to build out the other races and areas of the story. hehe. Now you talk about a challenge. Wow, that's a challenge. But so far it's been unbelievably fun!!
I can't wait to do my next novel, of which ironically enough, I've already got the notes for. It's called "Symbiosis", but I won't say much more. You'll just have to wait till I write it.