That used to be the case, but there were reports of it not working anymore a few months back. Search for threads on this.

I've got a solid history of checking lots of bags. One way of getting around the 70lbs rule is to check all the heavy bags as belonging to the 1K. And make sure you check in together at the 1K desk if there is one.

You can also try emailing 1K voice to ask about this. If the response is in your favor, print it and bring to the airport.