  The radiative emissions in the ee$\in$MC generator are extended to include
the Initial/Final-State radiative diagrams, with Initial-State/Final-State
interference, for the NLO and NNLO calculations and the Initial-State radiative
diagrams associated with the NNNLO calculation for $e^{+}e^{-} \to
\mu^{+}\mu^{-} (n\gamma)$ and $e^{+}e^{-} \to \tau^{+}\tau^{-} (n\gamma)$
Events. The NNNLO Initial-State radiative diagrams represent the largest
contribution to the perturbative Feynman series in the emission of 4
hard-photons. From the convergence of the total cross-section for $e^{+}e^{-}
\to \mu^{+}\mu^{-} (n\gamma)$ and $e^{+}e^{-} \to \tau^{+}\tau^{-} (n\gamma)$,
we estimate an uncertainty on the theoretical error corresponding to the
truncation of the perturbative Feynman series as a function of the soft-photon
cut-off applied in the exponentiation using the technique described in [1]. We
discuss how this estimation procedure of the theoretical error associated with
the truncation of the perturbative Feynman series can be extended to most
experimentally measurable physical observables and the potential pitfalls of
this strategy.
