this is the best conservative estimate of how many planets have complex life like ours: 1429 planets

For the Universe, the galaxies are our small representative volumes, and there are close to 10^11 to 10^12 stars in our galaxy, and there are perhaps something like 10^11 or 10^12 galaxies. With this simple calculation you get something like 10^22 to 10^24 stars in the Universe. This is only a rough number, as obviously not all galaxies are the same, just like on a beach the depth of sand will not be the same in different places. 25 percent of Sun-like stars have planets. This means there are at least 100 billion stars with planets in our Galaxy. With about 100 billion galaxies in the observable universe, suggesting that there are at least 10 trillion planetary systems are in the Universe. http://arxiv.org... "what's the probability of life forming? one in seven billion" Considering what we know (or rather lack of) about Abiogenesis, applying "odds" to the event seems somewhat strange (despite what creationists would have you believe :P). So what do we know then? Habitable zones are the best guess approach to determining possibilities of life. These habitable zones exist as a range from the sun in which water can be supported on a planetary surface. Additional factors normally include a super giant gravity well that in essence protects the habitable zone from comets, asteroids etc. Habitable zones however are not stable creatures. They are dependent on what life stage their sun is currently in. Stars like our Sun go through three stages that could foster life. The first lasts about 10 billion years while the star burns hydrogen in its core. Our Sun is currently in such a period, called the "main sequence", and the Earth lies within this stage's habitable zone. The zone extends from just within Earth's orbit to nearly the orbit of Mars (or 0.95 to 1.37 astronomical units, with 1 AU being the distance between the Earth and Sun). When the star begins to burn its hydrogen in a shell around a growing helium core, it brightens and expands and becomes a sub-giant. The habitable zone sweeps outward, extending from 2 to 9 AU. The inner edge of this zone remains habitable for several billion years while the outer extreme, where Saturn currently orbits, is habitable for a few hundred million years. The star then fluctuates in brightness for about 20 million years as it switches to burning helium almost exclusively, before becoming a red giant and swelling to 10 times the diameter of the Sun. For about a billion years afterwards, the habitable zone around the red giant extends from 7 to 22 AU, the outer edge of which lies beyond the orbit of Uranus. So planets that are currently very cold and icy can warm up and become potentially habitable. This shows the time period over which these conditions change is very long - long enough for life to form ( comparing that with the time it took for life to emerge on Earth - an estimated 700 million years). Habitable zones are as much an issue of placement as they are of time. The chances of life forming increase. Due to the limits of technology, the types of planets we can detect are limited (large gravity well Jupiter sized planets). Computer modelling offers the best solution to determining probabilities of habitable zones. Current modelling estimates arrive at a rate of 25-50% of extrasolar planetary systems will have a habitable zone capable of supporting an earth like planet (Giant "super earths" i.e. rocky planets the size of Jupiter are also being discovered with increasing frequency). Adding to the chances, we must consider aspects like Jupiter's moon Europa, which is thought to have a subsurface ocean with an environment similar to the deep oceans of Earth. Venus once had a climate similar to Earth's and vast oceans of water. Recent Mar's photos show water formed canyons, deltas and waterfalls. We also know life can be supported in scalding, acidic hot pools, in the driest deserts, and in the dark, crushing depths of the ocean. It has even found a niche in the frigid polar regions, in toxic dumps and nuclear power plants. Undersea hydrothermal vents also support entire ecosystems. Hydrogen and oxygen are the in the top 3 most common elements in the universe. Of the top 3 elements they are the only two to form a compound. That being water. So as for your "best conservative estimate", I would say you are quite a far ways behind.