Keep the stakes live, and know when to stop

A player who cannot affect the outcome has stopped playing, and an evening that has curdled will not be rescued by finishing it.

The quiet failure mode of a mixed group is the player who is mathematically out with an hour still to go. They keep taking their turns, politely, and they have stopped playing. Whatever the rules say, a person with nothing left to influence has become an observer performing participation, and everyone at the table can feel it even if nobody troubles to name it. The evening does not collapse. It simply goes flat, and afterwards that person is a fraction less enthusiastic about the next one, usually without being able to say quite why.

The remedy is to build in something for them to want. Handicaps agreed openly at the start are the blunt tool, and they work considerably better than their reputation suggests, provided they are offered without pity. Teams of mixed strength do the same job. So do side goals, personal targets and running counts that persist beyond a single result, giving a trailing player something real to chase in the last hour. So, most simply, does choosing games in which a losing position keeps genuine influence over how the thing ends.

The other half of playing well is knowing when to stop. Somewhere in a long session the enjoyment can drain out, and almost nobody says anything, because finishing feels like a duty imported from contexts where finishing matters. It does not matter here. The result exists only inside the agreement, and the same people who made the agreement may dissolve it. When turns get slower without getting more interesting, when the talking stops, when a rules dispute acquires an edge it would not have had an hour earlier, someone should say shall we leave it there. Stopping while people still like the game is precisely what makes them want to play it again.