Different Sim different relationship Type
second example
@SalixCatI'm also experiencing this issue for several months already. Here is what I deduced.
The traits of the other sims affect the duration of the relationship event. Say, I'm doing a friendly story and the Outgoing trait of my sim decreases the time of the event. Similarly the Outgoing trait of the other sim is supposed to decrease the time of the event (at least that is what was happening before). But I think some of the winter's updates removed this feature. The event card will still say the old duration, but the actual time would remove that boost from the trait of the other sim.
In the video below, you can see that the event card says 41 minutes for an event, but then it shows 48 minutes. The other sim has a relevant Alluring trait for this romantic story.
This happens with the sims of other players (the ones which have relevant traits) or with your own sims (like adult NPCs you haven't promoted who has Good Upbringing trait or retired sims).
Edit: I'm not sure why the video shows up really small. I will include screenshots below.
Here are the screenshots
