I don't disagree, but I definitely do not agree fully with your sentiment. "theft" implies a loss to the owner. (and sorry to folks in the other side, "piracy" also implies theft/loss)
So if folks can sit on top of a skyscraper and look into a ball park to watch the game, it's not theft, but they are enjoying something of value without paying for it, and society generally accepts this behavior in that case. But not if you splice your neighbor's cable to watch for free. (is that even still possible?)
Maybe call it, "involuntary gratis"? It implies some harm, but not on the same degree as theft.
All indefinitely means is "not certain". So it could mean a week... Or a century.
These disks are pretty well understood. You should be good for a decade. At about 12-13 years it's risky and anything after 15... If it's still working, count yourself lucky.