A bottle cap of water is enough. A blocked gutter is a hatchery.
Mosquitoes complete the egg-to-adult cycle in as little as eight days in warm weather, and they only need still water to do it. The usual suspects on a residential survey are blocked gutters, plant saucers, unused paddling pools, tyre swings, birdbaths that are never emptied and the tray under an air-conditioning unit.
Source reduction beats spraying every time. Empty or refresh anything that holds water weekly, screen your water butts, and keep gutters clear through autumn. Barrier treatment on foliage helps with adults that fly in from elsewhere, but it will never outrun a breeding site in your own garden.