For me the only organising i tend to do is book a plane ticket and then the rest comes after i land. Might set up a vt meet aswell in advance, but i never book accomodation or tours in advance. And i often have 4-5-6 plane tickets booked at the same time and i hardly have a day in life where i am not seaching for plane tickets to far flung destinations.
My trips these days tend to be for only 2 months and usually i start searching for promo tickets well in advance. In Sept i will got to India for 6 weeks, spending a month in sikkim. This involves purchasing 8 air tickets, Puerto Princesa to Manila, to Bangkok to Kolkota to Bagdogra and back again. I purchased BKK - KOL return with Airasia Thai perhaps 6 months ago and just last week i managed to get a promo tkt with Cebupacific BKK - Manila which was the last of the 8. But i have been researching places to see, accommodation, trekking agencies, restaurants etc for 6 months. When i return i will start researching next years trip and looking for promo tkts, which will be to Myanmar. Actually i have a few notes in my trip planner already so i guess the answer to your question would be 2 trips at a time (planning)
We are 5 in my family, so planning a trip takes long :) but my all time best is 4 trips at the same time and this is for this year.. It is very busy one as in the middle of all the traveling we moving country and continent... But I always keep my eye for promotions and if I see something interesting (cheap flights) to a country I want to go, most times than not I buy the tickets and than I look for hotels and such. Tours are done on the ground, as often is much cheaper to get good tour locally.
I am so disorganised (no laughing at the back you VTers) it is all I can do to plan one trip at once, but I have one in the planning stage now. Watch this space.
I write wonderful tips in my head as I am going through a spot. Then I sit down to the computer later and cannot even begin to know where to start....
I think 4 trips organised in advance is the most I have done so far. I have 3 organised at the moment, and that is pretty much my norm.
You people are all too organised, it is all I can do to decide what to do tonight! I still haven't, for the record.
It's not really 'me' but I haven't got much choice 'cos available dates are fixed and it's always cheaper to book flights well in advance. I'm looking forward to a time when I can be more flexible.
I usually organize a trip per time.