One of the things I've found troubling about the search for extra-terrestrial intelligence is the very narrow band in which we classify 'life.' Most usually it's done on our own terms. We think of aliens as being roughly our height with some sensory apparatus and then tack on various appendages and spikey or round bits to make them seem alien.
To me these archetypes have never been alien. They're more like invented animals - what-ifs about our own biological environment and its potential evolution either future or in an alternative past. Real aliens wouldn't even acquiesce to the same rules that we do. I remember reading some time ago an anecdote that I often quote that if single-celled organisms of the type we know and understand were to have evolved on Venus then equivocally, they would be made entirely of glass and be the size of a large house.
And that's supposing they exist on the same biological plane. Edwin Abbots' Flatland is a parable that could excitingly be taken literally as well as the satire of Victorian society and analogy of physics it so often is. What if, in another part of the universe, mathematics is sentient? What if geometry is it's way of physical representation and interaction? Once this kind of lateral thinking is applied to a universe that is near infinite in scope and 13.7 billion years in age then suddenly the 'Goldilocks' representation of aliens is really rather inept - an outward visualisation of our own insecurities rather than realistic or considered interpretation of the forms that the broadest definition of 'life' probably takes.
Consider the experiment often used by hard sci-fi - if were to encounter an entirely mechanised planet where no 'life' in biological terms exists but a machine intelligence, perhaps not even sentient, governs it's ecosystem would we call this life? What if, in a more Iain Banks style, aliens are huge creatures without any defineable anatomy that stride whole solar systems in single steps?