Which Brief for me...?

Favourite types of briefs:
Short sharp or long and meaty, something to get your teeth into?
This is my debate. Recently I've been doing this 'book of 100' brief and I've had it for the best part of 8 weeks and yet I'm still not happy with it, still havent pulled my finger out and done enough work, and still havent got any further in packaging it. Thus not got it finished. Might I add, I now have to design a set or series of posters for the 'release of my book' which is this friday ontop of finalising the book itself. Not feeling overly confident about it...however since my last post I have FINALLY finished the video.
I'm beginning to think that perhaps short, sharp briefs are more for me. After having a few long briefs set at college, I find myself wasting my time, not getting in depth research done and basically fannying around. This had made me think perhaps theyre not best suited to my way of working. Maybe the short snappy ones are more me. That aside though, I dont always feel I work to my potential when I do short ones so perhaps I'm just being difficult and am somewhere in between of the two...