I have found that whenever "Time dependent" option is turned on, which according to help:
Select the Time dependent check box if your problem is transient (i.e., unsteady), and specify the analysis physical time in the Total analysis time box, the time step of results outputs in the Output time step box.
After completing the Wizard, you can modify these settings in the Calculation Control Options dialog box.
The calculation becomes much slower. Without this option, a simulation converges typically in less than 200 cycles, and the Solver's Info window does not display the real "physical time", but merely CPU time; When this option is on, what previously takes two minutes could increase up to like ten minutes.
What is the nature of turning on "Time dependent" option? if it is merely to prevent prematurely stopping the simulation, then it is merely a "non-stop" option. But from the significantly lowered simulation speed it seems that something else is also happening. What is happening behind the hood with this option?