When to stop using the Lumi Staff

[Haldour]

I remember reading a post a while back that I cant seem to find about the point when using a lumi staff is outweighed by the number of casts it takes to kill a mob at a certain HP vs the med time and use of higher level AE nukes for quadding. Somebody with math skills that far outweigh mine did some magic, but every search i do comes up empty handed. Any of you folks out there ever do the math and figure what HP point is or know that link? Really appreciate the help.