Did some checking, if I have this right, PTSC can continue litigating for damages for some time after patent expiration:
Link to below: http://www.generalpatent.com/faqs/expired-patents
Expired Patents
What if my patent has already expired? — You may still be able to collect some past damages if your patent expired less than six years ago.
U.S. patent law allows a patent owner to collect damages accrued up to six years preceding the filing of a lawsuit. For example, if your patent expired a year ago and you filed a lawsuit immediately, you may be able to claim damages for the five years preceding its expiration.
