All, It is best to look at what the life-environment requiremnt is for the assembly. In parts of this industry we qualify the solder and assembly by aging at 200oC for 200 hours and then cycle for 100 cycles -40 to 200oC using 6 hours per cycle ( 2 hours top and 1 hour bottom). This represents the operating environment that the assembly will experience. Surprisingly, some of the soft solders do survive, but not Sn63. I would do the pre-cycle aging if the operating environment is maybe 100oC, but would use 125oC for a 200 hours. The thermal aging induces many of the metallurgical changes that the assembly may undergo in its lifetime, and shortens the test time need to qualify a product. (the poor ones fail early and drastically). The thermal aging oven time is cheap. If operating temperatures are lower, there is no need to have the higher temperature, I use operating temperature plus 25oC. No scientific basis, but it has seems to work. Phil Hinton