Duration
Duration is a type of card that was introduced in Seaside. Duration cards are Action cards which usually have an effect on the turn after they are played. A duration remains in play until it is no longer doing something. The durations are
A Haven played with no card in hand to set aside, an Outpost played on the second (or more) consecutive turn of a player, or a Tactician played with no cards in hand to discard will be cleaned up (discarded from play) at the end of the turn when they are played; in all other cases, the duration will stay in play until the end of the turn after it was first played.
When you Throne Room or King's Court a Duration, the Throne Room / King's Court also stays in play until the Duration is cleaned up, to remind you that the Duration's next-turn effect needs to happen twice or thrice. When you Procession a Duration, the Duration gets trashed, but it still has its next-turn effects, and the Procession remains in play until the time at which the Duration ordinarily would have been cleaned up if it remained in play.