It's been a few years for me, but I had purchased new tabs early for my Roadster and put them on the car...then sold it before the old tabs expired. I was able to get a refund. But the person I corresponded with said I was only able to get the refund because I sold it BEFORE the new tabs took effect. Once the new tabs take effect...there are no refunds. And the new owners can't use your tabs. It's just gone.
As I said, it's been a few years, so things could have changed. And I could have gotten bad information. As I recall, the info on the DOL's site wasn't terribly clear.