  We present up to two decades of spectroscopic monitoring of the double-peaked
broad Halpha emission lines of seven broad-line radio galaxies. These extremely
broad, double-peaked lines are successfully modeled by emission from gas in the
outer accretion disk, and their profiles vary on timescales of months to years.
This variability is a valuable probe for understanding the structure and
dynamics of the accretion disk. We characterize the long-term broad-line
profile variability in detail, and compare the evolution of the line profiles
with predictions from a few simple physical models for dynamical processes in
the accretion disk. We find no evidence for persistent, periodic variability
that would be indicative of a precessing elliptical disk, or a circular disk
with a long-lived, single-armed spiral or warp. We do find transient, periodic
variability on the orbital timescale, possibly resulting from shocks induced by
tidal perturbations, and variability in the wings of the profile which suggests
changes in the emissivity of the inner accretion flow. Dramatic but localized
profile changes are observed during flares and high-states of broad-line flux.
In 3C 332, these changes can be explained by a slow, smooth, secular change in
disk illumination. In Arp 102B and 3C 390.3, however, a simple disk model
cannot explain the asymmetric profile changes, suggesting a need for more
sophisticated models. We also observe sharp, transient features that appear in
the blue peak of the objects, which require a well-organized velocity field.
