Hi! I did the Norwegian, Swedish and Italian course. The Norwegian one was extremely long and although I am free with my time and worked on it pretty much every day, it took my 6 months to complete. In comparison the Swedish and Italian course were done in no time and my fluency level is "only" about 30 %. Is that because they aren't as long?
PS: By the way, duolingo is absolutely fantastic. Everybody I show it to loves it. Imagine they had taught languages like this when I was in school. I would be fluent in 10 or more languages today. Even so, I learned more languages after I turned 40 then before. And they say the older you get the harder it is.
I think the Norwegian tree was updated at some point to include more skills, as was German and probably a couple of other trees, so that's why it was longer.
As for fluency, I think that's only an indication of how strong your words are, which is to say (pretty much) how golden your tree is. It's not a number I entirely confide on, and I personally tend to ignore it most of the time.