Hi, have not tried this exact case, and my experience is from years ago.
But have on a couple of occasions, I had let my plan expire. The recordings remained. And I could access them even when I could not access any channels. I remember the STB having an internal storage.
Even if things have changed, I think it would be safe to go ahead, as long as you keep the STB and your subscription.
Recent users can update details about the storage in current boxes.