  Fusion frames, and, more generally, operator-valued frame sequences are
generalizations of classical frames, which are today a standard notion when
redundant, yet stable sequences are required. However, the question of
stability of duals with respect to perturbations has not been satisfactorily
answered. In this paper, we quantitatively measure this stability by
considering the associated deviations of the canonical and alternate dual
sequences from the original ones. It is proven that operator-valued frame
sequences are indeed stable in this sense. Along the way, we also generalize
existing definitions for fusion frame duals to the infinite-dimensional
situation and analyze how they perform with respect to a list of desiderata
which, to our minds, a fusion frame dual should satisfy. Finally, we prove a
similar stability result as above for fusion frames and their canonical duals.
