Off-hand, I'd guess ten years minimum? No clue for sure, but I haven't exactly gone looking.

To be fair, he is doing everything he can to set us up for a good grade, and doesn't want us to use ChatGPT for any actual work that we would hand in (studying essay formats aside), so it's within his MO, but like. As I said above, he's a philosophy teacher, encouraging his students to outsource thinking. Yes, ChatGPT is easier than going to the writing lab or getting an actual human tutor, but still! You'd think he could provide a sample essay or something instead.