Un-Canceled: The first three books of the Liaden series did not sell well enough for the original publisher to want to commission sequels. Disappointed, the authors got day jobs and went on with their lives for the next several years while, unbeknownst to them, a significant Liad fandom was growing on the Internet (to the point where "When will the next Liaden book come out?" was a question in the SF fandom newsgroup's FAQ).
When the Internet arrived in Lee & Miller's neck of Maine, they were startled to find that not only were fans clamoring for the next book, but the title of it, Plan B, had already been decided for them. With this fandom behind them, Lee & Miller were able to find a publisher to continue the series, and cranked out seven more books (as well as two collections of the short stories they continue to self-publish in chapbook form every year).
Then the series was uncanceled again when Baen picked it up after that other publisher, Meisha Merlin, went out of business. Four more books were added to the series (though two of them had already been written as fan-funded draft manuscripts), then other sequels and prequels were contracted. To the fans' delight, the series now shows no signs of stopping.
Write What You Know: Sharon Lee has worked several positions in academia over the years, including administrative aide to a dean. This might help to explain why a number of Liaden stories are set at colleges or schools of one kind or another, and why those settings all feel so authentic.