I like those exercises. I have slowly gotten a stiffer and stiffer neck over the years (I am approaching 68). It has coincided with taking up cycling ten years back. I think the primary culprit is the looking up/ahead position I ride in. Some of the suggestions here feel like they may help. Another exercise I learned from an Alexander Technique instructor is to lay on my back with the back of my head elevated by a few books for 15-20 minutes. I use this position while meditating and feel like I have gotten some improvement from it.