Here's the policy from Northwest Airlines:
Coach Class: Each ticketed passenger is allowed two (2) pieces of checked luggage.
Each piece: 50 pounds (23 kg) with linear dimensions not to exceed 62 inches (158 cm).
[b]Exceptions for trans-Pacific travel wholly between U.S./Canada and the Philippines, China and Hong Kong, checked pieces may weigh up to 70 pounds (32 kg) each.
Checked luggage within the free 2 bag allowance that weigh more than 50 pounds and up to 70 pounds will be assessed a $50.00 heavy bag fee.
Once you get here to the US, Northwest only allows one checked bag per customer, with each additional bag charged $25. Other airlines charge between $25-100 per extra bag, so if you can get away with only one bag, try to do so.
When Menci comes home with me next month, we've got the problem solved. She will need three bags - she collects blue jeans. We'll use my allowed bags for her excess. I'm just taking clothes for my visit that I don't mind throwing out to make room for her belongings.

It sounds just like what I did in my apartment too!
Cheers,
Rob and Menci