On "almost" a daily basis now. I was a big fan of quora, and spent quite some time there. I liked this niche community, where more importance is given on generating content. (Also it's kinda hipster, lol). How much time, well that depends.
If I am in the mood for a #goodlongread then I spend a good hour or so, else I just browse through random posts, add random comments. I am still easing my way into writing regularly and probably use it to just vent out my thoughts, ideas and feelings over the internet. I think Hubski will soon be a part in that expression. Only time will tell!
So the reason why we seek out the so-called "hipster" things is because we inherently want to be different from everybody else. It is a way of screaming to the world, "HEY GUYS!! LOOK I AM UNIQUE!!" It is just us trying to make a place in this universe, just elbowing our way in an already crowded place, trying to stand out among the masses. Plus I am not a big fan of crowded places, yes even on the internet.
Speaking as someone who can remember the event that triggered the origin of the Eternal September event, yea, bingo. This what I wish I was creative enough to put into words. Digg was great before the infux. Reddit was amazing before it started to get super popular and it got harder to find the people worth talking to. Snapzu is way to hipster for me, but there are people worth talking to there. Voat was becoming a neat community before all the FPH flooded the place. I think that Hubski has, by the nature of how it is set up, the ability to absorb the floods of people and have them self-select out so that the people who will enhance the community will stick around. at least that is the hope.