I work with a nonprofit that is negotiating a (standard length) 75 year lease for a piece of parkland. The nonprofit will have to invest many millions of dollars into buildings and improvements on this land (all publicly accessible). Without the 75 year lease, there is no way the nonprofit could run a capital campaign to raise money for the improvements - nobody would be willing to donate money if in a couple years the government could choose to change their minds and rip up the contract. This type of dynamic exists (someone else needs to make a huge upfront capital expenditure, and they need some sort of guarantee that they won't get "rug pulled") all over the place.
Case in point, in 2017 Austin leased part of the airport for another company to run as the "South Austin Terminal". The original lease was for 40 years, and then only a couple years later the city changed their mind and decided they wanted that land back to do a major overhaul of the airport, and they tried to get it back with some extremely shady eminent domain tactics (and they basically got their ass handed to them in court). I actually hate the South Terminal (it's confusing and not connected in any way to the major Austin airport), I'm glad to see it go, but I'm also glad the city can't weasel their way out of a bad decision just because they changed their mind: https://communityimpact.com/austin/cedar-park-leander/transp...
I agree that there needs to be some way to hold previous office holders accountable for decisions that affect a locale long after the original signers are gone, but just saying we can only have leases for 20 years or so isn't the right way to do it.