Will December too late for winterizing (Northern New Jersey)?

We live in the northern portion of New Jersey. Our lawn care provider, Scott Lawn Services, applied Turf Builder Pro Winterizer on Dec. 10, 2007 and insisted that the timing was appropriate, even though we had measurable snow on Nov. 10,18, Dec 2, 4, and 5. I am wondering if our lawn can really benefit from it as suggested.