AFAIK the Power Company hadn’t yet ceased supplying GDC so there was no need to seek specific performance. The Court declared the contract to continue to apply and so the Power Company continued to supply the electricity at that rate.
The most recent refernce I can find to this situation is a 2007 Commerce Commission decision which indicated the contract was still going on then.
Things have been complicated by changes to the electricty industry in NZ since the original decision (in brief a company can be a supplier or lines business but not both). GDC built an aquatic centre and ice rink in 2002. This brought their annual usage up to 2.5GWh, which is cut-off point between being a lines business and supply business. The Power Company (as a lines business) would then be over the threshold and in breach of the regulations, so the council sought an exemption from the commerce commission which was denied. As best I can make out, the Power company can now only supply up to 2.5GWh per year under the old indefinite contract.
But I would argue that copyright law indirectly recognizes that a corporation may last forever. Copyright law time-frames are based on the life of the creator but what if a corporation is the creator? Could Disney theoretically hold on to a copyright forever? The answer is no, but that had to be specifically written into the law.
In the US, mineral rights are severable meaning an owner can sell them apart from the land itself. If you (or any previous owner) didn’t sever the rights, you still own them.
It occurs to me that the United States itself is presumed to be eternal. Emphases added in italics.
The 1777 Articles of Confederation referred to the “perpetual Union between the states.”
In 1783, George Washington wrote that the first thing “essential to the well being, I may even venture to say, to the existence of the United States as an independent power [is] an indissoluble Union of the states under one Federal head.”
After the Constitutional Convention of 1787, James Madison wrote to a friend at the ratifying convention in New York that ratification was to be “in toto and for ever.”
After the Whiskey Rebellion in 1794, Washington wrote of his satisfaction that “my fellow citizens understand the true principles of government and liberty [and appreciate] their inseparable union.” As new states and their citizens joined the Union, Washington said the nation should bind “those people to us by a chain which never can be broken.” In his Farewell Address of September 1796, he wrote, 'To the efficacy and permanency of your Union, a government for the whole is indispensable."