For many systems, the work values' standard deviation (σ) is small, i.e., σ ≤ 2 k B T even for the shortest switching length of 5 ps. There are, however, three noteworthy exceptions: Defining a variance threshold when unidirectional non-equilibrium free energy estimates become unreliable is complex. Different research groups have proposed varying thresholds, ranging from values for the standard deviation of the work and ∆U distribution from σ = 2 k B T to 4 k B T . However, it is essential to note that these thresholds are not immutable values and may depend on the specific system and simulation conditions.