We know 336 patent will expire in 2015. With so many companies still at large and less than two years left, we all have a reason to worry how speedy TPL can extract value from this patent near the end of it life.

So I did some search on the exforcing bility of a patent and find this one -

http://www.patentspostgrant.com/lang/en/2011/03/patent-reexamination-of-an-expired-patent

"Of course, it is perfectly appropriate for a patent to be reexamined after expiration. In fact, the USPTO provides a separate claim interpretation standard for such cases. Unlike reissue applications, which cannot be pursued after expiration, patent reexamination is based upon the enforceability of the patent. The period of enforceability is determined by adding 6 years to the date of patent expiration. 37 C.F.R. § 1.510(a)

Looking only at the filing date, the ‘086 patent would seemed to have expired on November 24, 2006. However, this patent’s term was extended, due to the regulatory review delay of the Food & Drug Administration. The extended expiration date of the ‘086 patent is September 24, 2010. Thus, the ‘086 patent remains enforceable (for past damage purposes) until September 24, 2016."

Two main things of above is 1) "The period of enforceability is determined by adding 6 years to the date of patent expiration." Patent owner can demand royalty or sue infringers for damage within the 6 years period after the expiration date of a patent. 2) within this 6 years, patent owner can bring inter party re-examination to PTO for possible favorite claim scope changes (need more DD on how this works after the expiration date.)

Nano