as for "dramatic deadlines", I use them as little as possible. I know i hate them as a player because they feel cheap and artificial, like things will turn out a certain way regardless of the adventurers' actions.
I understand what you are saying and see your point but Dramatic Deadlines (i.e. turning up at the most dramatic moment) can be important from a story point of view.
It is just more exciting if the group arrives at a scene just in time to have a chance to stop the evil maniacs dastardly plan, rather than they arrive in plenty of time and put a circle of protection on a key location rendering his plans mute.
I agree that this sort of thing is artificial, but it isn't necessarily cheap. It does require a certain level of the suspension of disbelief however which will vary from group to group. Of course the suspension of disbelief can only go so far, if the group has a rough deadline (accurate to within a day or so) and miss it then I agree that the opportunity is wasted and the plot changes accordingly.