Historical maximum lease time
A 99-year lease is, under historic common law, the longest possible term of a lease of real property. It is no longer the law in most common law jurisdictions today, yet 99-year leases continue to be common as a matter of business practice and conventional wisdom.
The law.
Under the traditional common law doctrine, the 99-year term was not seriously literal, but merely an arbitrary time span beyond the life expectancy of any possible lessee (user) or lessor (owner).
William Blackstone (1723–1781, of "Commentaries on the Laws of England" fame) states that a lease was formerly limited to 40 years, although much longer leases (for 300 years, or 1000 years) were in use by the time of Edward III. The 40-year limit was based on the text "The Mirror of Justices" (book 2, chapter 27).
In the law of several US states, a 99-year lease will always be the longest possible contract for realty by statute, but many states have enacted shorter terms and some allow infinite terms.
Due to the influence of the ideas of Henry George at the time the Australian Capital Territory (ACT) was established in the early 20th century, all land in the ACT is held under 99-year leases, the first of which expired in 2023.
The 99-year lease concept has been more common under the civil law regimes when it comes to concessions of territory: most concessions last for 99 years.
References.
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