Several times more planets could increase the probability of a distant civilization several times, at the most. That is not a lot, if the initial probability is already tiny.
A rocky planet with no metals have a much weaker magnetic field. A civilization without iron and other metals is more difficult as well. Without heavy radioactive isotopes, volcanoes and tectonics is also different or non existent.
May be some other factors, not all against aliens.
Several times more planets could increase the probability of a distant civilization several times, at the most. That is not a lot, if the initial probability is already tiny.
A rocky planet with no metals have a much weaker magnetic field. A civilization without iron and other metals is more difficult as well. Without heavy radioactive isotopes, volcanoes and tectonics is also different or non existent.
May be some other factors, not all against aliens.