If we know that the material can go 10k years without degradation, which is something we can know, then it can last that long. Will it be practically possible to store it in a way that will allow for the maximum amount of time before the material begins to degrade? That’s a whole other thing.
This is just what goes on in medicine science when things are operating properly. Test, collect data, run experiments, do it again, do it again, then, after the short term use has been proven safe 30 different times, by 100’s of research groups, you start researching the long term affects of it.