Radioactive atoms, in the aggregate, don’t have a half-life. If you measure the nuclear radiation coming from a heterogenous glob of radioactive material, and it takes N hours to drop to 50% of that level, then it will take more than N hours to drop to 25% of the original level. The original material had both shorter-lived substances with a half-life of less than N hours and longer-lived substances with a half-life of more than N hours (and possibly non-radioactive elements as well), and since the former materials decay faster than the latter, the ratio between them falls until the latter materials dominate.
Radioactive atoms, in the aggregate, don’t have a half-life. If you measure the nuclear radiation coming from a heterogenous glob of radioactive material, and it takes N hours to drop to 50% of that level, then it will take more than N hours to drop to 25% of the original level. The original material had both shorter-lived substances with a half-life of less than N hours and longer-lived substances with a half-life of more than N hours (and possibly non-radioactive elements as well), and since the former materials decay faster than the latter, the ratio between them falls until the latter materials dominate.
I suspect the same process holds true for facts.