  While high-resolution cross-correlation spectroscopy (HRCCS) techniques have
proven effective at characterizing the atmospheres of transiting and
non-transiting hot Jupiters, the limitations of these techniques are not well
understood. We present a series of simulations of one HRCCS technique, which
combines the cross-correlation functions from multiple epochs, to place
temperature and contrast limits on the accessible exoplanet population for the
first time. We find that planets approximately Saturn-size and larger within
$\sim$0.2 AU of a Sun-like star are likely to be detectable with current
instrumentation in the $L$-band, a significant expansion compared with the
previously-studied population. Cooler ($ \rm T_{eq} \leq 1000$ K) exoplanets
are more detectable than suggested by their photometric contrast alone as a
result of chemical changes which increase spectroscopic contrast. The $L$-band
CH$_4$ spectrum of cooler exoplanets enables robust constraints on the
atmospheric C/O ratio at $\rm T_{eq} \sim 900K$, which have proven difficult to
obtain for hot Jupiters. These results suggest that the multi-epoch approach to
HRCCS can detect and characterize exoplanet atmospheres throughout the inner
regions of Sun-like systems with existing high-resolution spectrographs. We
find that many epochs of modest signal-to-noise ($\rm S/N_{epoch} \sim 1500$)
yield the clearest detections and constraints on C/O, emphasizing the need for
high-precision near-infrared telluric correction with short integration times.
