This document discusses simulations of the advanced Galileo constellation performed by DLR Gesellschaft für Raumfahrtanwendungen (GfR) mbH. It describes a multi-level training process for Galileo control centers using flexible simulations. The simulations have increased in complexity from 2011 to 2013, mirroring the growing Galileo constellation. Lessons learned from simulations and early operations will influence future simulations to make them more realistic through approaches like multi-center operations concepts and automated command sequence generation.