However, in each island of stability the most stable element is much less stable than the most stable element of the previous island of stability. Therefore in most higher islands of stability the decay times will become too short.
It is possible and rather likely that only the first undiscovered island of stability may contain relatively long-lived elements, e.g. with half-lives over one second.
An island of stability finishes at bismuth, which is radioactive, but which has a huge half-life. The next island of stability contains the long-lived thorium and uranium and the still relatively long-lived neptunium and plutonium, after which the half-lives decrease very quickly.
Whichever will be the longest-lived elements of the next island of stability, their half-lives will be many orders of magnitude smaller than those of thorium and uranium.
Nevertheless, it was usually supposed that 126 is the next magic number for protons, in which case it has not been reached yet. Other possible values, from more recent computations, are 122 and 124, also not reached yet.
Moreover, the isotopes that are the most stable for the already synthesized elements are expected to have more neutrons than in the isotopes that have been successfully produced. So it is not impossible that an "island of stability" might have already been reached, but only with isotopes that have so few neutrons that they remain outside the zone of stability.
https://en.wikipedia.org/wiki/Island_of_stability