[Treadmill]

I have some forty foot pine trees (spruce??) along one side of my lot which I am very concerned with. During the recent windstorm, the tops were bending at least 4 to 5 feet and should any break off, quite likely would reach my neighbors patio.
Can anyone give! me some expert advice as to when to 'prune' them and how much can be cut off the tops without killing the tree.
Any and all advice is much appreciated.