One part of the game I find frustrating is when one player does not manage to find all his clues, and then the game stops, period.
"What, we played an hour just to stop like that?"
More than the frustration, the said player feels guilty of this early ending.
To prevent that, we play with a special rule:
At the end of the 7th hour, if some mediums did not find all their clues, they lose 1 vision card for each missing clue. For example, if a medium should have seen 2 vision cards, but is missing his weapon, he'll actually see 1 vision card. It's possible to see 0 cards if the medium did poorly, he'll be voting randomly then.