I read your posts this morning, yes, retesting everything makes no sense. But the FAA is judge and jury and if they tell you to run it again, you run it again.
I have read that $100 million is required to start an airline. FAA is federal, money means nothing to them. Money cannot be used as a reason to complete evac demonstrations more frequently.
Your analogy is good, now just change it so that each time a lug nut fails, you also have to pay for testing all parts again.