Hi Lara,
If you haven't already, check out the documentation below on bounces. While all bounces and their responses can be unique based on the responding ESP, in my experience, Invalid Domain, Account Disabled, and Refused are all soft bounces that typically end up in a hard bounce state. That said, normally the amount of bounces gets hit within a day or two, so your particular use case is unique in my experience.
I don't know if anyone else has a similar use case and can speak to their experience.
https://experienceleague.adobe.com/en/docs/deliverability-learn/deliverability-best-practice-guide/m...