The calling of a fiction writer, particularly a fantasy writer, is to know a little bit about a lot of things–just enough to be dangerous, so to speak. I tend to read survey books that talk about history–things that give overviews, such as the history of warfare, or the history of the sword, or navigation. I would say I do a fair amount of research, but mostly it’s an attempt to dump as much into my brain as possible for spawning stories and writing about things intelligently. For Mistborn, I researched canals, eunuchs, and London during the mid 1800’s.
How much time do you spend on research?
That one’s really too hard to judge.
Research for me is ongoing for any given work, and I don’t track how much time I spend on it. Generally, I dig into specific topics when the need arises, then do more ‘cast out the net’ general reading for ideas the rest of the time. Generally, I’ll only dig in deeply if a topic is important to a specific story (such as the Mistborn examples above).