Who serves Greenbay / Appleton? I'd build on your United Miles. IMHO, they've got better planes (E+ for elites) and a better alliance (star vs. skyteam) than Northwest. United also seems to have frequent promotions; although I don't follow NW's promos.

Check the MileagePlus website. Between credit cards, online banking, investing, etc. you could probably triple your current mileage balance without flying at all. Combine that with your planned flight activity and you'll have a nice balance in a year.