I always like to approach development from the perspective of what can I get away with to achieve the same effect?
The near and far clip planes, together with the planes defined by the field of view of the camera, describe what is popularly known as the camera frustum. Unity ensures that when rendering your objects those which are completely outside of this frustum are not displayed. This is called Frustum Culling. Frustum Culling happens irrespective of whether you use Occlusion Culling in your game.
Think of creative ways to avoid using Update and see how your performance improves.