Optimal intermediate states would minimise the standard error of the overall free energy estimate for a given total sampling time. However, selecting these would require knowledge of the statistical inefficiencies and divergences of the probability distributions along all possible paths between end states. It should be noted that the optimal path is influenced by the relative efficiencies of sampling at intermediate states, and is therefore dependent on the sampling methodology as well as the Hamiltonians. It appears challenging to obtain this information without costly simulations which would reduce overall efficiency. Nevertheless, a number of approximate approaches have been developed.