Frequency of price pulsing

I recently experimented with price pulsing by dropping a book down to free for a few days and tripled my sales for the month! Needless to say, I’m planning to continue price pulsing my backlist and I’ve listened to Thomas’s podcast episode on it.

How frequently can one price pulse though before readers just wait around expecting it? I plan to run at least one sale on one book every quarter. With a backlist of nine books, I might try to do it more frequently. I just don’t want to create a low anchor price point for my stories in my readers minds.