Oh, an idea, perhaps, to change the balance, consuming clock could also add a cat? To actually make eating the cheese or clock a dilemma? Or have another cat chase the cheese as well? Or, different types of cats (but this might take away the charm of its simplicity).
The clock definitely adds to the fun and extends the game. However, currently I think it is not really a dilemma. If you have the patience to take 10, 20, 30 clocks every once in a while there is always enough clocks that took less time to fetch than the time they add. In other words, if you keep eating clocks frequently enough, you probably always have enough time to add a few extra cats.