I play with few molds, with many multiples copies of each.
I have multiples mostly for practice purposes, since I am still learning.
They are also helpful, as mentioned above, so you can play discs in various stages of wear.
Also, you will learn alot by learning to throw all shots with one mold rather than relying on a disc for each situation.
It would also help with consistency.
Wizard | Buzzz | TeeBird | Firebird