Hi Tim,
Yes it's happened to me on amyfront 105 deraileuer about the same age. Its essentially just metal fatigue from bending and flexing over the years. My deraileuer started shifting poorly before it finally snapped. Lubing the pivot points on your front mech will help reduce this kind of wear and tear.
Nothing to worry about. Your deraileuer had a good life
![Smile :-)](./images/smilies/icon_smile.gif)