Whats the point of endurance?
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During endurance you can stack cards with multipliers for an efficient way to farm for Reputation for the shop. (It goes through 3 loops stacking all modifiers gained. It is possible you experienced it ending after a single loop which is an uncommon bug which has since been fixed... i believe.)
Completing endurance will also flag the girl as "impregnated" (seen by the white smile by their icon in the menu) . At the moment this flag does nothing, but it will likely have an effect on endings in the full game.