I almost never complete a Hub in one sitting because of the research involved and the work of creating the best possible title, tags and summary. And often it takes a while to find an appropriate illustration. A Hub usually takes me at least three sittings.
When I get the idea I quickly write a title and then a partial draft or outline. That can take as little as half an hour. I can always stay up half an hour later to get this done.
Then, when I have bits of time, sometimes as little as 15 minutes, I will seek out and compile factual information. I often have ideas for refining my draft when I'm away from my computer. I always write these ideas down and keep the notes near the computer.
Then when I have a good block of time -- it can be a day later or a month later -- now that I have all the material I will rewrite and put my copyright and contact info on it, and complete the summary and tags and links, mount the photo, and tweak the title. I'm always tempted to post right away, but it is best to go do something else and return to the piece and re-read it one last time for clarity and style.