why the purelight process seems endless

#1 pureLight never stops, it bakes until you're happy with it. You've done over half a million baking passes at 4 texels a pass ... I usually call it quits before 100 using 16.

It does mention this in the manual.

#2 It is an iterative process, it will keep on baking until you end it. If you are doing an automated bake via the command line, you can use the -passes flag to set a number of passes for it to stop after.

#3 I bet your scene is awesomely lit, though, after two weeks...

#4 lol

#5 oh god , yes, the scene looks very bright, I'm still curious about the result after one year process. hehe