If you know what most of the pinball name abbreviation names are....
if you print out custom apron cards years in advance before you even purchase an already released game,
if you start designing custom rooms/buildings just for the collection of pinball games,
if say to yourself "just one more game and that will be it",
if the value of your spare parts on hand are relatively equal to (or more than) the value of your collection,
if you purchase the same title more than once,
if driving across town to buy gas is bothersome, but driving hours across state lines to buy a game is perfectly fine,
if paying for house or car repairs is too expensive, but adding another game to the collection is not,

Oh well, it's all fun...