In the Quartus® II software, when the 'Optimize multi-corner timing' option is enabled on the Fitter Settings page, the Fitter will optimize designs for both the slow-process, high-temperature timing corner and the fast-process, low-temperature timing corner. In 65-nm and newer technologies, there is also a slow-process, low-temperature timing corner available for analysis with the TimeQuest Timing Analyzer. However, the Fitter does not optimize designs based on this timing corner.
This problem may be fixed in a future version of the Quartus II software.