How to decide the production time in the free energy calculations?

hello everyone,

I am calculating free energy using thermodynamic integration. I have 24 intermidiate lambda states starting from 0 to 1. For each lambda state an equilibration of 100ps followed by a production run for 1ns is performed. Should I increase the production time from 1ns to 10 ns for each intermidiate lambda state to get better results? provided my system contains 127160 atoms. This is a large system so do I need to increase the production time? I am decoupling 1 water molecule from the system.