"The study of events behavior through real simulations could contribute to develop or improve Future Event Set (FES) data structures in order to achieve better performance on large scale simulations. In this paper we have analyzed FES data structures of two discrete event simulators: CD++ and NS-2. We have run variety of simulations on each simulator to describe a real event behavior by observing event timestamps, life times into the FES and firing time (event execution time). The goal of this research is to present new ideas on how the FES data structures could be improved exploiting event behaviors."--From the paper.