I'm so glad you liked it!
To answer your question: depending on how convoluted you want your Matriarch's assignment to be, it could take you from a couple sittings to a dozen sessions. Here's what my gut tells me:
- Exploring a single dungeon could take 1-2 sessions. Not every dungeon has Relics. Not every Relic can be found in dungeons.
- Travelling between two settlements and dealing with episodic encounters along the way could take up to 3 sessions, depending on how far apart they are.
- Solving a crisis as described in the Events section could take 6-12 sessions by the time they come to fruition during the campaign, depending on the size of their Pool.
The game is a work in progress, its rhythm and everything else might change with the coming update of Boundless and my desire to allow for solo play. But if you have the opportunity to give it a whirl, I'd be more than glad to hear your feedback!