I feel that passive lasers (those that serve only as aesthetics) should not consume any fuel (or at least an almost imperceptible portion) since when using them constantly, I consume fuel very quickly when their function is not even to provide thrust, it has happened to me that I leave them on to mark something specific, and in a while the fuel is already depleted, I would recommend increasing the ISP in enormous quantities and reducing the thrust to zero if possible (if not, to 0.00000... and so on) Just so the lasers can stay on for much longer.