I’d add that compared to my previous airline, the process of swapping trips you don’t like / didn’t express a preference for is pretty good - it’s mostly done online, and there’s a decent app which provides easy access to what’s available, and what people are looking to swap. As others have already said, there’s enough people looking for different things to make the swap system work pretty well, at least on the 320 - can’t speak about any other fleets.