Performing 3 more independent replicas with the TIP3P water model yielded nearly identical results -the 4 replicas agree with each other up to an R 2 of 0.99 and three of the four replicas have the same R 2 with the experimental HFEs (0.84, SI Fig. ). Only replica 3 has an R 2 of 0.83, indicating that few new ligand conformations are sampled by the additional replicas or that if new conformations are sampled, these are isoenergetic with previously sampled conformations. While it is generally recognized that multiple short simulations are more efficient in covering conformational space than one long simulation , our results demonstrate that this general rule has to be applied judiciously -there exists a threshold in time below which additional sampling becomes inefficient, failing to reach new energy basins from the conformational landscape, all the while adding computational costs.