It depends on whether or not the FAA puts a time limit on the certificate. If they time limit it, the certificate will say NOT VALID FOR ANY CERTIFICATE AFTER xxxxxxx. In that case, the company would know if they ask for a copy of your certificate. The issue then becomes one of the FAA saying you are fit to fly and if the company says you cannot work they are discriminating aginst you. A legal mine field for companies. Most of them defer the decision on fitness to fly to the FAA.