First, stable "livable" planets. This is subjective, based on what sort of life-form is going to live here. Be it humanoid, microbial, vegetable, or whatever. Depending on what you or other consider as life, the possible stable habitats for life could be many, or few.<br /> I consider microbes a life form, so I would guess (based on antarctic and sea floor volcano info) that there are numerous extraterrestrial habitats where microbes could survive. Let me Clarify that numerous in this instance is not meant to represent a very large number (like say, 95% of all worlds being habitable).<br /><br /> Next, brief terms of evolution, longevity, and survivability. Stars do and don't survive for long, based of course on the type of star. It may take thousands to millions of years for a life form to come into existence (let alone evolve). By this time, larger stars usually die out in supernovae. Though I believe any sort of planet around a stellar giant is bound to be less than habitable anyways (I may be wrong).<br /> Light mass stars tend to last longer, and are more numerous (I think). They'd be the candidates for life more than the super giants, I believe.<br /> Evolution is another thing (and is braking into my final point). Species may be wiped out, before they have a chance to evolve, by cataclysmic events like a meteor strike, rampant volcanism, or other galactic dealies. They may not be able to adapt to new or frequent changing surroundings. Or the planet may somehow change composition and "die". Its a play against time, and adaption.<br /><br /> Finally, intelligent life. Can intelligent life be regarded as creatures serving in a simple societal system? Or do you require it have knowledge of simple tools, and very basic understanding of the surroundings? Or must they be close to our level of intelligence of questioning mind, matter, and space? Whatever the case, I'd say the chance for a creature with a bug-like behavior, and instincts, coming about it is at least some