Vanilla Co. Puff

When you look at powders or pressed powders, you end up using a puff, right?
As many of you may already know,
They say it's good to change this puff often, too, haha.
There is only one puff included in each product, you know.
So I buy some refills in advance.
I've noticed that some people replace it periodically or wash it before using it.