Yes, I invest 3 months each year, from September through December, planning my goals and methods for the next year. This year required some deep self-re-evaluation. But it moved quickly, and the plan is in place. I have a great year, and a great decade, coming. (To learn more, read my hubs on the 7 Habits of Highly Effective People.)
I agree with aLifeOfDesign said about writing being crucial. But, I've found that, for me, writing is not enough. If I want to succeed, I find it necessary to write my plan and then read it aloud to myself every day. I've been doing that since 1997. Big difference!