The Fixed Period [A Whisky Priest Book]

Britannula, off the coast of New Zealand, is a thriving republic. Three decades ago the government of energetic young men decided that compulsory euthanasia after the age of 67 would spare unnecessary suffering and state expense. But now, in 1980, some of those once-young politicians are now elder statesmen, facing very significant birthdays...

Trollope's only science-fiction novel, The Fixed Period is a satire on utopian dreams which he published in his own 67th year.