Frankly, not that often (the last time was 2016). We're alert for it, but when pub dates change, it's not usually quite this dramatic.
However, it is a disruption and it complicates things a hair, so it's not our favorite thing. Our favorite thing is reading the books, not having them pushed out of reach!
Questions? Let us know; you can reply directly to this email!
currently reading Kazuo Ishiguro's Never Let Me Go, which was published exactly when it was supposed to be