The effects last until the end of the battle.
It returns to normal after the battle ends.
The effect increases/decreases more with every repeated occurrence.
Increases are limited to 2x the character's stat (e.g. if their defense is 100, it can only be raised to a maximum of 200).
Decreases are limited to 30% of the character's stat (e.g. if their defense is 100, it can only be reduced to a minimum of 30).