You would also have to measure and account for over how much time the free users convert to paid users. If it happens over two years, you have to take that into

You would also have to measure and account for over how much time the free users convert to paid users. If it happens over two years, you have to take that into account. As the gigaom article mentions: The thing is, over time inactive users drop off, and active users start paying. Once Evernote finally figured that dynamic out and started talking about it, term sheets and partnerships requests started flowing in, Libin said.