I sample the wort when it goes into the primary and when I transfer. If the ferment seems to be stuck, I'll draw additional samples, maybe every other day. If I'm dry hopping in the secondary, I might draw a sample after a week to check hop levels.
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