This is a more interesting question.
In an ideal world, the size of a game would never matter – only the number of objects visible at any given time. (Out-of-scope objects should not slow anything down.) I6 was pretty good at this, but I7’s library has some problem points that loop over the entire contents of the game.
I have an experimental extension which fixes some of these points and partially fixes others. See this thread: Improving performance for large games
EDIT-ADD: It’s not updated for 6L02 but I could work on that if somebody needs it.