Can it still be mounted?
They'll last years that way.
Also, I believe most taxidermist will be honest with you. If it won't turn out or is damaged they'll usually let you know.
I had my oldest son's Drake Wood Duck in the freezer for years. I didn't store it the right way, and the taxidermist was up front and honest and told me it was not worth the time or money. He did share the zip lock / ice trick with me.
I kept a bass in nothing but a bread-bag for I think 4 years at the bottom of a chest freezer. Frost bit, broken fins the whole thing. Eventually took it in and its one the best mounts I have.
Its all about who you take it to.