  We present gray gas general circulation model (GCM) simulations of the
tidally locked mini-Neptune GJ 1214b. On timescales of 1,000-10,000 Earth days,
our results are comparable to previous studies of the same planet, in the sense
that they all exhibit two off-equatorial eastward jets. Over much longer
integration times (50,000-250,000 Earth days) we find a significantly different
circulation and observational features. The zonal-mean flow transitions from
two off-equatorial jets to a single wide equatorial jet that has higher
velocity and extends deeper. The hot spot location also shifts eastward over
the integration time. Our results imply a convergence time far longer than the
typical integration time used in previous studies. We demonstrate that this
long convergence time is related to the long radiative timescale of the deep
atmosphere and can be understood through a series of simple arguments. Our
results indicate that particular attention must be paid to model convergence
time in exoplanet GCM simulations, and that other results on the circulation of
tidally locked exoplanets with thick atmospheres may need to be revisited.
