I think that a patent is ''good'' for about 30 years. For example, a Chinese company called Qshave is making a copy of German Merkur Futur safety razor, which made its debut back in the 80s. The Chinese variant is not similar, it's 99% the same, and l believe that there can be only 30% overlap. The handle is a bit thinner, and the lettering is laser etched, not engraved like on the German razor, so more than 30%, right? The Germans can't sue them because the patent had expired a couple of years ago, so basically anyone can make those razors now.
That makes me think that Polaroid has no grounds for a lawsuit, and needs some pocket change, so they try to unearth something that can't really hold up. I believe some sort of settlement will be achieved between the two.