I think you're wrong.

http://www.finnegan.com/resources/articles/articlesdetail.aspx?news=140d86d1-9b54-4789-9562-ef18d15d0cb4

"Section 287 of the patent statute provides that a patentee, or its licensee, "may give notice to the public that the ... [patented article is] patented, either by fixing thereon the word 'patent' or the abbreviation 'pat.', together with the number of the patent." In the event of a failure to mark, damages may not be recovered "except on proof that the infringer was notified of the infringement and continued to infringe thereafter.""

Again, damages accrue only upon notice. That's when the damages clock starts. If you first notice up a potential infringer after the patent expires, they'll laugh at you and tell you to go pound sand.