At least technically, the U.S. can claim is has an open-ended lease on the Guantanamo Bay site via an agreement signed in 1903 with the Republic of Cuba, which

At least technically, the U.S. can claim is has an open-ended lease on the Guantanamo Bay site via an agreement signed in 1903 with the Republic of Cuba, which has no expiration date. For the bases in Chad in Niger, on the other hand, there is no such agreement. The right to operate is entirely "at will" and can be revoked by these governments at any time. As it appears they just did.