Your situation may be different - I assume you are trying to maximize pups. In the tropics the issue is the opposite - too many pups and then the bunches and fruits tend to get smaller and smaller each year. By the time of the first harvest, we tend to have at least 5 healthy pups fighting for the space that had originally been ideal for just the 1 that was planted.
To get to your question ... the assumption/prejudice is that the old mother corm is part of the problem, that it will continue to pump out the pups. Nothing great, and it may not help with your decision, but here are a few pictures about how to remove the mother corm:
Picasa Web Albums - Ray Grogan - Banana
(I never have, but I bet others have - you could probably plant the mother corm in some other location where you wanted more plants and see what happens. I would be interested.)