After your flight lands you’re supposed to keep your seat belt buckled until the pilot parks at the gate and turns off the seat belt sign. Although if you’ve been on any commercial flight in the past decade you know that’s not what happens.
At the very latest once the plane stops (you might still not be at the gate, and will move again) passengers start to take off their seat belts, gather their belongings and sometimes even make their way into the aisle.