When is PAO overkill?

For short numbers or one-off items — a plain peg or the Major System alone is faster to use and needs no composite.

PAO's payoff is compression at volume. To remember a 4-digit PIN or a single 2-digit number, building and decoding a composite is more machinery than the job needs — just use a Major-System word or a simple image. Reach for PAO when you're storing a lot (decks, long numbers) and the reduced image/locus count actually matters. Match the tool to the load.