For me, it was gradual. I had had random bouts of insomnia for awhile, and realized those correlated with days I had caffeine after 4 PM or so. So I cut back to

For me, it was gradual. I had had random bouts of insomnia for awhile, and realized those correlated with days I had caffeine after 4 PM or so. So I cut back to noon, which improved it, then cut back to the morning, which was even better, and then just cut out caffeine entirely. I've never slept better.