I usually start something, then think about another cool map halfway thru and start working on that. Then i get caught up playing matchmaking so no maps will ever get done. So basically it takes a long while for me
Usually in big chunks. I try to do as much as I can in as little time possible, but I end up doing small amounts in a long amount of time. I find that people who draw out a plan of their maps can get things done faster, because they know exactly what to do and where. I have a habit of going way off what I originally planned, letting my improvisational skills take control, thus taking up more time.
I get random ideas and then I make a map and I work on it like 2 hrs a day, so bit by bit. I have a life... sorta
Long sit downs. Sometimes it's the other way around but I don't really care. Bit by Bit is often away to forget something you forget to write down (I don't write crap down)