https://www.theregister.co.uk/2018/10/04/macos_mojave_overview/

Review Apple takes great pride in shipping macOS annually, as regularly as clockwork.

Only a few macOS updates have failed to arrive in the window between July and October each year – and those were a very long time ago. 10.4 Tiger, which followed its predecessor by 18 months, arrived while Microsoft was in the middle of its Longhorn agonies, the six-year lacuna between XP and Vista, with Apple taunting Microsoft: "Redmond, start your photocopiers."