Calculate battery duration
Average current is given by

$$ I_{AVG} = \frac {80m  \times 8}{30 \times 60} = 0.35 \ \text {mA} $$



Figure 1. The Duracell AA Plus Power quotes for currents down to 5 mA continuous.

This shows that at 5 mA you can expect > 500 hours. You'll have to extrapolate for your load conditions.