Commercial/Industrial Temperature FPGA - Using Same Configuration

If you don't want to resynthesize it is possible to run a TimeQuest analysis on a different grade and different temperatures. Have a look at the documentation for the set_operating_conditions tcl command in Timequest. That way you can know if your compiled design can be safely run on a different grade.

AFAIK Quartus by default compiles for the worst conditions, i.e. slowest timing in the grade you specified for setup requirements and highest timing in the whole grade range for hold requirements. So you should be safe.