This may have been asked (although I don't think it has), but does anything limit the number of times you can use the response on the Steed of Imladris? The text is:
Response : After attached hero commits to a quest, discard a card from your hand to place 2 progress on the active location.
As the card is restricted, it is not very good unless you can choose to discard many cards to add lots of progress to the active location (otherwise, I'd probably not bother with it). As far as I know, Responses like this are not limited. Of course, I'm doubtless wrong about this, but I can't think of any reason the response here is limited except by number of cards in hand.
Obviously I'm thinking of Erestor here, as this is a huge boon to questing through some locations.