As I understand it, the pixel light count doesn't limit how many can be in a scene. It limits how many can be illuminating any single vertex. So if you find yourself needing more than 6 in your scene, think about limiting where the lights shine. For example use spot lights rather than point lights, so each light is only illuminating the surfaces you intend it to light, with no unintended spillover. A couple point lights off in the distance may not be providing useful illumination to a specific part of the scene, but they still count towards the light limit.