I said "Other"
Because while I go through phases (like now) where I will work on developing a particular section of the setting 30 minutes to several hours everyday - once I get a level of detail I want for the region, I run a campaign in that general area and do little to no development until I know that either I will be starting a new campaign in another part of the world, or the current group is going to be visiting an area that requires development.*
I have been working on and playing in Aquerra since the summer of 1989 (when 2E came out) so whole sections have had both various tweaks and total overhauls over time. These days, I take chapters in the DM's Gazeteer that were 8 to 12 pages and expand them into 70 pages or more. For example, when I re-detailed the Archduchy of Wallbrook, I took the original 5 or 6 pages of info and made it into 80 pages in the process of a few weeks. Currently, I am redoing the Magocracy of Thricia - originally, that section was 9 pages of info. I added two more pages during campaigns I ran in the early 90's and then added another 4 pages at the end of the 90's - but so far in the revision I am at 81 pages and about halfway done (maybe slightly less than half) which I have done over the last month and a half or so.
I also occasionaly tweak around areas of Aquerra I am not planning I am running a campaign in, but usually I end up abandoning those projects, leaving a skeleton that can be fleshed out at a later date (which in a way, I guess that is what those early chapters were).
So anyway, it is hard to say how much time overall. . .
* of course character actions can force me to have to develop further while the campaign is running.