Our models work to the extent the need to - i.e. predict decay over a relatively short time frame.
That is, in the code, a static variable.
This is because they don’t care about 50 years from now.
What works for 50 years probably doesn’t for 500 Million. The universe is full of examples of this effect.
Did you know man flew heavier than air aircraft for TENS of YEARS before the correct model of even WHY an airplane flies was proposed?
Just because you can correctly predict a BOOM does not mean you know everything. In fact, science is based on the understanding that we probably don’t understand everything properly, yet.
What is the purpose of assuming that what we haven't had time to observe will be contradictory to and orders of magnitude outside the range of what we do know and have observed?