  According to the currently accepted paradigm compact steep spectrum (CSS)
sources are precursors of larger/older objects and gigahertz peaked spectrum
(GPS) sources may be earlier stages of CSS sources. In this paper we confront
this paradigm with the outcome of recent observations of CSS sources that are
significantly weaker than those known before. In particular we claim that not
all CSS sources must end up as large scale objects; if the activity phase of an
AGN's central engine is shorter than the lifetime of a large scale radio source
(up to ~10^8 years) the radio source associated with such an AGN decays
earlier, e.g. at the CSS stage. We point out that a theory of thermal-viscous
instabilities in the accretion disks of AGN may explain many features of radio
sources at all stages of their evolution.
