One solution outlined by Jayanam is to animate the position and rotation of the camera. The trick is that you will probably have to go into the Curves editor and switch the interpolation of the keyframes to CONSTANT, otherwise the camera will move instead of standing still with a jump at the keyframe.
Another solution is to have separate scenes. Blender files can contain multiple scenes, each with their own camera and time line. Because the time lines are independent, this is usually the best choice. That way if you have to stretch out one scene, it doesn't force you to audit the other scenes to make sure their keyframes are still right.
You could also have multiple independent blender files and use linking to share meshes between them (or appending if dealing with the restrictions of a linked mesh become inconvenient).
After you have created several different scenes you can glue the rendered PNGs together in the VSE (again, in its own scene) to make the final video.