Yup, a long-haul or a cheap non-Lufthansa European break would do it. I'd go for SAS or Austrian destination that involves a connection. Helsinki via Stockholm or Copenhagen on SAS should do it, about £150incl, or Salzburg via Vienna on Austrian, about £190incl. 4x800=3200 in each case. For bonuses, you might want to remember that double destinations miles offer on UA flights until February; a cheap LHR-IAD trip would cost about £260incl and give you about 7,200 status miles and about 14,400 award miles.