[Unanswered]  How legal is a worn Impact Drake?

Hi, So we all know Impact Drake is a strong blade, but I want to know how legal would one be if it was used in battles a lot and the Rubber wears out a bit.

Is it still legal? Or would you need to get a new one?
As per the rulebooks, a worn down part is no longer legal when there is a significant change in performance. So one could assume when the rubber wears down to the point it's no longer the main point of contact, it would be time to buy a replacement.