Palaeoseismic evidence suggests that earthquake recurrence intervals in some regions can be highly variable, with clusters of multiple large events separated by much longer periods of quiescence. Because post-seismic processes have a significant effect on the reloading rate of the coseismic fault, we hypothesize that temporal variations in the amount of stress concentrated in the non-seismogenic lithosphere can modulate large earthquake recurrence times. We explore this hypothesis using simple analogue spring-dashpot-slider models. We find that in the presence of small amounts of environmental noise, post-seismic stress transfer over timescales much longer than an earthquake cycle may be an important factor in generating clustering behaviour. The propensity for the system to be clustered is a function of a non-dimensional number that we call the Wallace Number, W. W is defined as the average earthquake stress drop divided by the product of the long-term geologic strain rate across the fault and the effective viscosity of the system. Our results indicate that environments with relatively low strain rates and a relatively weak non-seismogenic lithosphere are most susceptible to clustering driven by post-seismic stress recycling mechanisms.