Our ability to discover planets is very new to astronomy as is
   the search for signs of ET life via new planet discoveries.*

   I think our criteria for "life" is very limited at the moment.
   Anthropomorphic bias: Things called "living" seem to all have at
   least SOME parallels to us humans.

   So yes, I think we're missing a lot.   Agreed. I think we need
   some advances in bridges between chemistry and biology. There's
   some speculative work done. For as long as I know there's always
   been a subset of scientists who believe that some forms of
   crystals may actually be living.

   The borderline of life/non-life is a fascinating field.