A hub should be researched before it's written. Me for example, I do a lot of researching but I break it down on the Hub so the average John or Jane Doe can understand.
You can have a lot of content on a hub, but if they (you viewers) don't understand it and it's concept their not going to enjoy.
For an affiliate marketer like myself, I rely on individuals buying products that I've used or heavily researched to earn a living, so I have to write hubs that can assist them or guide to them to something else in a concise, simple matter.
In short, I take about a day to research the fundamentals of what I'm going to write about the next day.