Radar bright lava flows in the Radunitsa Labyrinthus region of the Carson quadrangle on Venus traveled up to 200 km within a network of orthogonal grabens. Using a cooling model for basalt to evaluate the graben-channelized lava flow emplacement process, we demonstrate that the lava flows would need to either be very thin (<5 m) or have a very low effusion rate (<50 m3s-1) in order to cease flow within the observed 200 km solely by cooling. Neither condition is likely given our mapping observations and what is known about long lava flow emplacement on Earth, leading us to conclude that lava flow emplacement in Radunitsa Labyrinthus was probably supply- rather than cooling-limited.