I think intelligent life developing is directly correlated to how much available energy there is for that life to utilize.  Using us as an example, we were able to develop intelligence because our ability to acquire calories (energy) has increased in efficiency and efficacy over the years.  If a planet with life on it has conditions that make acquiring energy difficult, this would (in my opinion) affect how likely intelligent life is at developing.<br>As far as how that affects estimates, I don't know.  I don't know how many habitable planets would be considered 'ideal' based on our planet vs just 'viable'.<br>It is always fun to speculate about these things, nice video!