1 million years would be pushing it, but there isn't a clear boundary. Eldred v. Ashcroft is the most authoritative case in U.S. law on this but it doesn't reach a clear conclusion. [1]
What's more interesting is the dissent in that case. According to Justice Breyer, the current copyright term is valued at 99.8% of a perpetual copyright (presumably because the present value of the future becomes increasingly discounted over time). Unfortunately, the rest of the court didn't go along with this as it would have implied throwing out plenty of prior copyright extensions as well.
What's more interesting is the dissent in that case. According to Justice Breyer, the current copyright term is valued at 99.8% of a perpetual copyright (presumably because the present value of the future becomes increasingly discounted over time). Unfortunately, the rest of the court didn't go along with this as it would have implied throwing out plenty of prior copyright extensions as well.
[1] http://www.law.cornell.edu/supct/html/01-618.ZO.html