Specify inflexible start or finish date constraints , if any. A battle plan lasts until contact with the enemy. The art of progress is to preserve order amid change and to preserve change amid order. Your friends don't need it and your enemies don't believe you anyway. Time is Nature's way of making sure that everything doesn't happen all at once.
Indecision is the key to flexibility.
Never tell everything you know. I love deadlines. I especially like the whooshing sound they make as they go flying by. If you kill me, I'll get in your way. If I kill you I'll get in your way.