  We consider soliton-like solutions of a variable coefficients, subcritical
nonlinear Schrodinger equation (NLS). In a previous result, we proved the
existence of a pure, global-in-time, generalized soliton with prescribed
asymptotic as t tends to -infinity. In addition, we described the corresponding
dynamics for all time, up to a small error term. In this paper we prove that
the soliton is never pure as t tends to infinity. Indeed, we give a precise
sharp lower bound on the defect induced by the potential on the soliton. This
result shows the existence of nontrivial dispersive effects acting on
generalized solitons of slowly varying NLS equations.
