  Characterization of exoplanets has matured in recent years, particularly
through studies of exoplanetary atmospheres of transiting planets at infra-red
wavelenegths. The primary source for such observations has been the Spitzer
Space Telescope but these studies are anticipated to continue with the James
Webb Space Telescope (JWST). A relatively unexplored region of exoplanet
parameter space is the thermal detection of long-period eccentric planets
during periastron passage. Here we describe the thermal properties and albedos
of long-period giant planets along with the eccentricities of those orbits
which allow them to remain within the habitable zone. We further apply these
results to the known exoplanets by calculating temperatures and flux ratios for
the IRAC passbands occupied by warm Spitzer, considering both low and high
thermal redistribution efficiencies from the perspective of an observer. We
conclude with recommendations on which targets are best suited for follow-up
observations.
