Top decile probability of death is 55 % over a decade or roughly 0.5 % per month. Thus, biden has 1 month to croak and trumpo has a year to croak, which leads to (1-0.995)*0.95+0.995=...=0.025% chance or 1 in 4000 for both to occur.
https://www.soa.org/resources/research-reports/2020/us-mort-rate-socioeconomic/
(the website data is more interesting than low probability of success)
No one said the expirations needed be natural.
But dems also researched immortal phylactery tech for presidents, so i think it evens out