After a certain amount of time things become "public domain" but I think the copyright laws ensure that something cannot be reproduced during the artists lifetime and their heirs, so that someone would have to pay royalties to the family for any use of the art.
The Sonny Bono act that was passed in 1998 actually extended that term for another 20 years. I'm not sure why they felt compelled to do that, perhaps because life expectancy went up - who knows! Hope that is what you were looking for.



