You make an excellent point. Companies could eg. have 25yrs to make a profit.

On the other hand: if an artist produces something that slumbers in anonymity for decades before it suddenly explodes into popularity and becomes part of the cultural canon, then I'd want the artist to reap whatever benefits possible. That is: if anyone is making big bucks off of that, it first and foremost should be the artist, for as long as they're alive.