Transition lengths of 100 ps and 200 ps are extremely unreliable with large MUEs (around 1.3 kcal/mol; less than half the complexes with UE < 1) and error bars (only around 3% of the complexes with uncertainties ≤ 0.5 kcal/mol). Further, around 30% and 15% of complexes have error bars greater than 1 kcal/mol using 100 ps and 200 ps respectively. Extending the transition length to 400 ps and beyond up to 2 ns, the accuracy and precision of ABFE predictions consistently and substantially improve with MUEs below 1 kcal/mol and zero complexes with error bars above 0.9 kcal/mol in all cases. Based on this analysis, it is clear that the minimum acceptable transition length is 400 ps.