So often here in Montana people like to take it easy and think that deadlines don't really mean anything. It was nice years ago when a handshake could seal a deal or you would sign a contract on the hood of your old pickup truck.
Well these times are gone, when there are deadlines and time frames you need to stick to them. When you are supposed to respond by 5:00pm you need to respond or give notice that you need more time. I do not think it is very professional to just get back to the other party when it is convienent for you. This happens too much and needs to handled better.