Remember in P&P, we are told that Mr. Bennet, "captivated by youth and beauty, and that appearance of good-humour which youth and beauty generally give, had married a woman whose weak understanding and illiberal mind had very early in their marriage put an end to all real affection for her". In "Persuasion", Anne Elliot actually hopes that Mr. Elliot (a very sensible man) will marry her sister Elizabeth before he discovers what she's really like, and in "Emma", Emma Woodhouse says something along the same lines.