A performance whether by movie, electronic, TV, etc. is protected under U.S. Copyright Law. This right can be sold or transferred by written contract. Thus, if the performer sold their rights, the heirs would get nothing. However, if they retained their rights the perfomance law states it expires after 50 years of its release. It's I believe a different right when it's intellectual copyright like your original composition or a patent.
There is probably also collective bargaining agreements by Actor's Equity, AFTRA and the Screen Actor's Guild. Those could be different rules from normal statute but is probably not less then the statute.
If I remember to ask, I do know an entertainment attorney so I'll firm this up the next time I see him.