For those of us in WA State. Here's the official requirements. Somewhere I remember that YOM plates needed to be restored by an established and licensed restorer, I don't remember but the plate I bought for my '47 Chrysler for $5 needed to be restored anyway.
It is registered to that car permanently with no renewal fee. Keep in mind there was a bill on the floor last year that ultimately failed even though one bought and registered their vehicle in good faith under those terms set by the Government. There were those in the legislature that wanted to renege on that agreement to require an additional fee so collector cars would be required to re-register every (x) amount of time (I don't recall) and pay an additional fee. I would not be surprised if that bill were to return in some other form in future legislative sessions.
Addendum: It is not my intention to introduce politics into this thread but merely to state the facts.
https://app.leg.wa.gov/rcw/default.aspx?cite=46.18.220