I worked in a C shop for like 8 or 10 years and we never introduced a back-wards incompatible API release. There were a few changes that required all servers to be restarted (not at once) to change network protocol (16-bit fields overflowing, that sort of thing). But it was inconceivable that you'd break something that is working. To be sure, we took a couple of weeks before designing an API, and for no one was the API they wrote and shared with others the first API they designed as an adult. Even when the implementation mutated out of all recognition, the API owner would just do whatever re-coding/re-implementation was needed behind the existing API.