Depends on who you are trying to get on with. If the company requires it, by all means go take it. FedEx (and I think) UPS require it to be current, and its only good for 2 years (I understand about the extension for continuously employed pilots, but neither company recognizes it), so you might want to wait until you are within a two year window or so of actually getting looked at by one of them. Nothing wrong with taking it and keeping it current just in case they or another company you are interested in that requires it starts accepting apps. Just keep in mind that you might have to retake it down the line to keep it "current".