Reading throught that article reminded me of all the crap Carl Segan used to spout off about in 'Cosmos'. Nucleur annihation is most unlikely. The most plausible explaination for why there is no signs of life on other worlds can be found by looking at our own. In the the approximately 4 billion years in which earth has been habitable, it took 3 billion years for life to evolve beyond single cellular organisms. This may have only happen because the conditions of snowball earth kick started evolution. Even then life did not necessarily favour intelligence, as dinosaurs had clearly not demonstrated anything that would lead to intelligence. It took an asteroid to clear the slate again and give large brained mammals the oportunity to evolve.
So it has been about 4 billion years to get to us. So how much longer will earth remain habitable? As the sun heats up the earth may have as little as 200 million years left. And I suspect that is exactly what happens with most planets, they simply run out of time.