  Compact Symmetric Objects (CSOs) are compact (<1 kpc), jetted Active Galactic
Nuclei (AGN), whose jet axes are not aligned close to the line of sight, and
whose observed emission is not predominantly relativistically boosted towards
us. Two classes of CSOs have previously been identified: approximately one
fifth are edge-dimmed and designated as CSO 1s, while the rest are edge
brightened and designated as CSO 2s. This paper focuses almost exclusively on
CSO 2s. Using complete samples of CSO 2s we present three independent lines of
evidence, based on their relative numbers, redshift distributions, and size
distributions, which show conclusively that the vast majority (> 99%) of CSO 2s
do not evolve into larger-scale radio sources. These CSO 2s belong to a
distinct population of jetted-AGN, which should be characterized as
``short-lived'' compared to the classes of larger jetted-AGN, as opposed to
``young''. We show that there is a sharp upper cutoff in the CSO 2 size
distribution at $\approx 500$ pc. The distinct differences between most CSO 2s
and other jetted-AGN provides a crucial new time domain window on the formation
and evolution of relativistic jets in AGN and the supermassive black holes that
drive them.
