Should not, if you still have ground missions with landed UFOs. The collection of items (e. g. the Elerium) and the kills should give you enough points. Only thing I really recommend to shoot down, are terror ships on terror missions. And one trick on top of that: If you don't research unrequired items (like alien food or Plasma rifle, if you prefer using heavy plasma anyways), then you will have additional points for collecting alien artefacts, most of the time. As much as this game is repetetive at it's core, you still have plenty of means to vary your game play.