We discussed this already a few thousand posts ago, but it was still unclear. I suggested to call a FSDO and get clarification.

FAR 61.39

(b) Notwithstanding the provisions of paragraphs (a)(1) and (2) of this section, an applicant for an airline transport pilot certificate or an additional rating to an airline transport certificate may take the practical test for that certificate or rating with an expired knowledge test report, provided that the applicant:

(1) Is employed as a flight crewmember by a certificate holder under part 121, 125, or 135 of this chapter at the time of the practical test and has satisfactorily accomplished that operator's approved—

(i) Pilot in command aircraft qualification training program that is appropriate to the certificate and rating sought; and

(ii) Qualification training requirements appropriate to the certificate and rating sought;

Now, the way I interpret the FARs, as long as you are employed/furloughed by a 121 or 135 carrier, in other words, you have a seniority number, it is still good. I'm not 100% sure if you can still use it if you go to another 121 or 135 carrier, but my guess is yes. However, if you decide to go back to flight instructing or do some other type of flying other than 121/135, it will expire! Again, call the FSDO or if you dare the "furlough committee".