Clusters and collision complexes are stabilized by three-body collisions that are two-step bimolecular collisions A + B --> AB* and AB* + M --> AB + M, where M is a bath molecule that removes the excess energy from AB. The lifetime of AB* determines the probability of a third-body collision; therefore, we have calculated binary collision lifetimes as a function of translational energy and temperature by quasiclassical trajectory calculations and compared the results with the analytical expressions of Bunker (J. Chem. Phys. 1960, 32, 1001). We find that the analytical expressions, which were developed for centrosymmetric potentials, are in poor agreement with the trajectory results of benzene/Ar for low values and in good agreement for high values of translational energies and temperatures.