Husbands and wives can own property jointly and transfer it between themselves in all sorts of tax-exempt ways, and it strikes me that these advantages could be exploited by what I'd call a "chain marriage". In a chain marriage, the spouses are of widely differing ages and the marriage exists purely for the preservation of wealth.
Example: A 60-year-old man marries a 30-year-old woman. When the man dies at age (say) 90, the now-60-year-old woman marries a 30-year-old man. No children (if any) ever inherit anything; instead, wealth is simply passed from husband to wife in perpetuity. Contractual arrangements could be made to prevent the younger spouse from leaving the marriage and taking half the money.
Has anyone ever done anything like this? Is this sort of exploitation simply too difficult to maintain for many iterations?
My law professor for wills and estates class always recommended this as the easiest way to beat the estate tax. Though he noted that many adults in their twenties seem uninterested in marrying septagenarians, no matter how large the tax savings.
The basic idea sounds similar to Heinlein's line marriage, from The Moon Is A Harsh Mistress.