The deploy that bundles three months of work is the deploy that fails at the worst time. Small releases fail small, and when they do, the cause is the last thing that changed, not a quarter of changes.
The discipline is unglamorous: merge small, deploy often, keep the delta reviewable. A release you can describe in one sentence is a release you can roll back in one command.
It also changes the psychology. When deploying is routine, it stops being an event, and the fear that makes teams batch changes into risky big-bang releases goes away.
