is choosing prompts to track for aeo still worth the effort?

It is if you keep the list small. Don't brainstorm prompts, steal them from real sources: questions from sales calls, support emails, and the question-style queries already in your Search Console. 20 to 30 is plenty. Phrase them how a person would actually type them into ChatGPT, which is longer and more conversational than a Google search. Then run the same list every month so you're comparing like with like.