According to the letter I have from the FAA, the ATP and FE writtens remain in effect as long as you work for a 121 air carrier or a 135 commuter air carrier. Employment does not have to be continous.
However 14CFR 61.39 (b) now states if you are working for a 121, 125 or 135 air carrier it is still valid. As long as you complete their PIC qualification training program.
Once you start the practical test, you must complete it within 60 days or you must retake the complete practical test.