I don't know anything about the f and k engines do they have rockers? If not then they aren't basically the same. There are loads more friction and ware points which is why the clearance goes out so quickly on the boxer. Unless your going round the world I don't think you need to worry about valve clearance even if they just double it. 12000 miles is a long trip even longer if it's moved to 18000. Do them as part of the prep for the trip at home and your sorted.