I'm going on year 8 or so and unlike many other hobbies I have never gotten tired of pinball. I love the many aspects of collecting, mechanical repair and playing too.
The physical and mental aspects of playing never get old. Its a great feeling to close off the outside world and get into a game to instinctively manipulate the ball flow using the flippers and subtle nudges together. I'd guess that this is the sort of zen feeling is what draws people into golf, pool, racing or whatever once they find something to connect with.