...
The "Balanced" optimization can take up to a few hours, depending on the boundary conditions, number of Events and the Complexity of the model. It provides a detailed/high resolution design proposal and the stress optimization goal is considered fully. More information about the stresses here.
The "Fine Tune" option takes the longest time and calculates a few more iterations than the Balanced option on the highest resolution level. Because of this it takes quite a bit longer in order to obtain a good printable surface and detailed structure of the result. The surface develops the most in these iterations.