  While previous studies have shown a strong preference for a future
mid-infrared nulling interferometer space mission to detect planets within the
HZ around M dwarfs, we here focus on a more conservative approach toward the
concept of habitability and present yield estimates for two stellar samples
consisting of nearby (d<20 pc) Sun-like stars (4800-6300 K) and nearby FGK-type
stars (3940-7220 K) accessible to such a mission. Our yield estimates are based
on recently derived occurrence rates of rocky planets from the Kepler mission
and our LIFE exoplanet observation simulation tool LIFEsim, which includes all
main astrophysical noise sources, but no instrumental noise sources as yet.
Depending on a pessimistic or optimistic extrapolation of the Kepler results,
we find that during a 2.5-year search phase, LIFE could detect between ~10-16
(average) or ~5-34 (including 1$\sigma$ uncertainties) rocky planets (0.5-1.5
R${}_\rm{Earth}$) within the optimistic HZ of Sun-like stars and between ~4-6
(average) or ~1-13 (including 1$\sigma$ uncertainties) exo-Earth candidates
(EECs) assuming four collector spacecraft equipped with 2 m mirrors and a
conservative instrument throughput of 5%. With D=3.5 m or 1 m mirrors, the
yield $Y$ changes strongly, following approximately $Y \propto D^{3/2}$. With
the larger sample of FGK-type stars, the yield increases to ~16-22 (average)
rocky planets within the optimistic HZ and ~5-8 (average) EECs. Furthermore, we
find that in addition to the mirror diameter, the yield depends strongly on the
total throughput, but only weakly on the exozodiacal dust level and the
accessible wavelength range of the mission. When the focus lies entirely on
Sun-like stars, larger mirrors (~3 m with 5% total throughput) or a better
total throughput (~20% with 2 m mirrors) are required to detect a statistically
relevant sample of ~30 rocky planets within the optimistic HZ.
