i don't think you'd need to be regular customer? i think it depends more on the SA. with both times i was given the booklet and cards, i was in different hermes stores (once in montreal and the other in london,UK) and both were my first visit to the store....and i only bought 1 scarf. i never mentioned/asked for the cards/bookelt though.
the SA in the hermes in selfridges was so kind, i bought 1 scarf and he gave me the cards and some kelly calache samples =). it was a very pleasant surprise and experience.