"And if you allow the lien to expire after 90 days without suing on it becomes invalid, the Owner can file suit against you in Court on a Petition to Release the Property from the Lien, and you may be liable for paying the owners attorney fees and costs if you do not record a release of your expired Mechanics Lien. If your lien has expired, it is thus best to record a lien release voluntarily."
http://www.hg.org/article.asp?id=21465