  Basing on the Gross-Pitaevskii equations, it is predicted that a repulsive
(defocusing) interaction makes a 2D polariton condensate able to accumulate its
energy under above-resonance optical pumping. The energy can be accumulated
during a lot of polariton lifetimes, resulting in the state in which the
mismatch of the pump frequency is compensated by the blueshift of the polariton
resonance. The process begins when the field density reaches the parametric
scattering threshold that is inversely proportional to the polariton lifetime.
Although the increase in energy may be arbitrarily slow in its beginning, it is
followed by a blowup. This scenario applies to the case of the transitions
between steady states in multistable cavity-polariton systems. There is a
tradeoff between the latency of the transitions and the pump power involving
them.
