Right now there's only a 24 hr, 3 day, and 1 week option for auto archive of any thread. This doesn't make any sense for events that users want to plan in advance. My friends easily will plan events most of our in-person events 1-2 months in advance so we don't want these threads to auto hide or people will forget they joined the event. These should only hide after the event is scheduled to end.
This is a Discord function, not something sesh can control, I am pretty sure. In the meanwhile, one workaround could be to have sesh "bump" the thread once a week (and I think delete the previous reminder?) by setting up "before event starts" notifications.