If you do play one you resolve it completely then play it a second time then play it a third time.
Dominion throne room duration.
This is good if you have a way to guarantee that this extra turn is still pretty good even with only three cards but weak if you end up having mediocre extra turns.
The throne room is always discarded during clean up if the duration is also discarded or otherwise has left play such as being trashed due to bonfire.
If you throne room a throne room which affects a duration the top level throne room does not stay in play and gets cleaned up during the clean up phase of the turn.
When you use a throne room variant on a duration it stays in play even if multiplying the duration s effect is not meaningful such as throning a tactician or throning an archive with 3 or fewer cards remaining in your deck.
Additional rules from the rulebook you pick another action card in your hand play it and play it again.
The second use of the action card doesn t use up any extra actions you have.
Playing an action card from your hand is optional.
You completely resolve playing the action the first time before playing it the second time.
Outpost is an action duration card from seaside when played it lets you take an extra turn albeit an extra turn where you draw fewer cards.
If you throne room a throne room you play an action doing it twice and then play another action and do it twice.
In all other cases the duration will stay in play until the clean up phase of your next turn.
If you use throne room to play band of misfits as a duration throne room will stay in play.