I believe infringement begins when one is put on notice. I have to go through my notes, but I remember from the TiVo trial that EchoStar was only liable from the first day TiVo notified ES they were infringing on the TimeWarp patent, and not one day before. We started sending out letters in I believe 2004? Can't remember, again I would have to go back and look through historical PR's. FWIW
Good luck to you, me, us, and all longs.