These belts are created (at least mostly) by Earth's magnetic field capturing or deflecting incident radiation, which therefore shields Earth's surface from the radiation and (I believe) protects life.

Earth's magnetic field isn't stable with time and has (geologically) frequent pole reversals. We don't have a great idea of how long this process takes, whether it is near-instantaneous or takes hundreds of years (or perhaps longer?). The poles are currently 'wandering' relatively fast and some geophysicists think this may be a sign of a pole reversal to come.

I wonder about how the Van Allen belts fair during a pole reversal, and if for some time interval the amount of incoming radiation on the Earth's surface is much greater, perhaps at dangerous levels.

Earth also has a much stronger geomagnetic field than other rocky planets because it has a solid iron-nickel inner core that rotates inside of a liquid iron-nickel outer core, inducing the magnetic field (the so-called 'geodynamo'. If the resulting Van Allen belt is indeed a safeguard to the development of life on Earth, it may be part of the reason that Earth is unique in life development versus its neighbors.