Ratio of the time to coalescence via gravitational-wave emission, parametrised by the orbital properties just after (T_post) and just before (T_pre) binary BH formation, as a function of f_kick := v/V_pre, where v is the natal kick vector and V_pre is the magnitude of the relative orbital velocity before binary BH formation. I illustrate three scenarios: natal kicks occurring either in the radial (solid blue), tangential (dashed orange), or polar (dotted green) direction.