Plan on a minimum of four weeks. That way, it should be done fermenting and the trub will be settled.
But, taking a gravity is the only absolutely certain method.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk