Allow me to draw your attention to Karl Marx' son-in-law, Paul Lafargue, who wrote an ode to laziness in 1883: "The Right to be Lazy", from a philosophical/economical/political/eschatological perspective (I wrote a small introduction here).

BTW, in my language, the inertia of mass is called "laziness". In a sense, Classical Mechanics explains how and why doing no more Work than necessary is entirely in tune with the way of the universe.

Also, as you say: if you're not lazy every now and then, you'll never feel the joy and fulfillment that results from kicking yourself in the ass and getting shit done.