Limited threat potential?

We’re getting all sorts of scare stories to the effect that currently non-existent bobbies on the beat are about to be replaced by drones. But let’s consider a few facts. A typical police drone can fly at about 40 mph and its battery will last for about 20 minutes. How much spying is going to be achieved in such a limited window? It’s about long enough to find the odd female sunbather au naturel and take a couple of snaps.