  High levels of dust have been detected in the immediate vicinity of many
stars, both young and old. A promising scenario to explain the presence of this
short-lived dust is that these analogues to the Zodiacal cloud (or exozodis)
are refilled in situ through cometary activity and sublimation. As the
reservoir of comets is not expected to be replenished, the presence of these
exozodis in old systems has yet to be adequately explained.
  It was recently suggested that mean-motion resonances (MMR) with exterior
planets on moderately eccentric ($\mathrm{e_p}\gtrsim 0.1$) orbits could
scatter planetesimals on to cometary orbits with delays of the order of several
100 Myr. Theoretically, this mechanism is also expected to sustain continuous
production of active comets once it has started, potentially over
Gyr-timescales.
  We aim here to investigate the ability of this mechanism to generate
scattering on to cometary orbits compatible with the production of an exozodi
on long timescales. We combine analytical predictions and complementary
numerical N-body simulations to study its characteristics.
  We show, using order of magnitude estimates, that via this mechanism, low
mass discs comparable to the Kuiper Belt could sustain comet scattering at
rates compatible with the presence of the exozodis which are detected around
Solar-type stars, and on Gyr timescales. We also find that the levels of dust
detected around Vega could be sustained via our proposed mechanism if an
eccentric Jupiter-like planet were present exterior to the system's cold debris
disc.
