This is a total WAG, but I would guess that it won't matter. I think anything patented runs out of protection in 17 years. If you did happen to encroach on somebody's patent, they'd probably send you a cease and desist letter as an introduction. AFAIK, there is no automatic penalty for infringing a patent accidentally, unless you were to continue to infringe after the other party informs you of the infringement. Even then, the penalty would have to be determined by a judge according to the damage caused by the infringement.