In detail, I plan my life 2 semesters in advance, which is about 6 months. (I'm just finishing up the rest of my plans for the year now.) In general, I've planned out up to 4 years, but those long-term calendars just never seem to work out in reality. I'm a computer geek, so placing everything in desktop calendars and coordinating them all through online services is easy for me. I always demand RSVPs from whoever I associate with well in advance, and I never change my plans at the last minute unless someone breaks their agreement. (Sometimes, they just mess up.) If I need to adapt or 'go with the flow', I don't handle it well at all.
This systematization allows me to perform a lot more research in my professional career than anyone I've ever worked with. I'm probably one of the most well-read people I've ever met, yet I still have 300+ books on my to-be-complete queue. (And no, they're neither fiction nor paperback.)
I'm not sure if this is a good idea overall, though. I do this now because as a kid I always wanted for something like this to exist. I hated not knowing what my day would include -- penciling in dates into a calendar never worked as it didn't really help me prioritize. But now that I've automated my entire planning scheme, I find it almost too easy to not socialize. (I plan my shopping around when I expect the stores to have the shortest checkout lines, my Netflix queue is full up, etc.) I'm trying to change this by assigning more of my planned time to the category 'socializing', but it's hard to get people to cooperate with my own scheduling needs. I want the ability to communicate better with people but am too addicted to the gains I get from studying so much. I'm at a loss on what to do -- so maybe I'm not great at planning after all. 
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Dum vita est, spes est.