I've said this before, but I like to think of it in terms of the old saying, "you can never step into the same river twice." This means, that as a river is constantly flowing and changing it's banks slowly wearing away parts and depositing more sediment in others, a pipe is also in a constant state of flux. It is never static. With each different tobacco smoked in it, rinsed or cleaned, cake cut back, wiped out, a pipe is always in flux also. I like to enjoy my pipes from the first smoke forward, and I enjoy how they change and evolve over time.
A bad tasting pipe at the start has happened for me recently, but in a weird kind of way, I enjoy smoking through that as well, like a sense of accomplishment once the bad taste is gone. I see it as a period of bonding with that pipe. Getting that briar into my DNA. A merger of man and tool. In that case, I see it not some much as break in, as much as merging... but, then I am the sort that loves the poetics of pipesmoking.