  The importance of long-period binaries on the formation and evolution of
planetary nebulae is still rather poorly understood, in part due to the lack of
central star systems known to comprise such long-period binaries.
  Here, we report on the latest results from the on-going Mercator-HERMES
survey for variability in the central stars of planetary nebulae.
  We present a study of the central stars of NGC 1514, BD+30$^\circ$623, the
spectrum of which shows features associated with a hot nebular progenitor as
well as a possible A-type companion. Cross-correlation of high-resolution
HERMES spectra against synthetic spectra shows the system to be a highly
eccentric ($e\sim0.5$), double-lined binary with a period of $\sim$3300 days.
Previous studies indicated that the cool component might be a Horizontal Branch
star of mass $\sim$0.55 M$_\odot$ but the observed radial velocity amplitudes
rule out such a low mass. Assuming the nebular symmetry axis and binary orbital
plane are perpendicular, the data are more consistent with a post-main-sequence
star ascending towards the Giant Branch.
  We also present the continued monitoring of the central star of LoTr 5, HD
112313, which has now completed one full cycle, allowing the orbital period
(P$\sim$2700 days) and eccentricity ($e\sim0.3$) to be derived.
  To date, the orbital periods of BD+30$^\circ$623 and HD 112313 are the
longest to have been measured spectroscopically in the central stars of
planetary nebulae. Furthermore, these systems, along with BD+33$^\circ$2642,
comprise the only spectroscopic wide-binary central stars currently known.
