Evolutionary tracks of e and P_orb under equilibrium tides for 0.3 M_⊙ + 0.3 M_⊙ binaries, over a grid of initial orbital periods and initial eccentricities. Each binary is initialized on a grid on the P_orb−e plane, and we plot the orbital period and eccentricity of each binary for every time step in COMPAS. The colors depict the age of each evolutionary snapshot in years. The binaries are only evolved up to 14 Gyr, approximately the age of the Universe. The top panel shows the period–eccentricity evolution under our fiducial tidal model, and the bottom panel shows evolution under the Z77 model. None of the binaries evolve meaningfully in this plane over their simulated lifetimes with the Z77 model.