In this contribution we illustrate some important features of the development of models for the simulation of advanced annealing processes. Taking arsenic as example we discuss the challenges that the last technology trends represent for process modeling. Issues like shallow implants, high doses, low total thermal budgets, and steep temperature profiles are discussed, highlighting the physical phenomena to take into account, and how to design models that reproduce them. We also discuss with examples how important are the critical evaluation of known parameters and established approaches, and the extraction of parameters from experiments. Finally we show some applications of our model for spike and flash annealing of arsenic implants.