Usually......it indicates that the engine has been run hot. This may have occured MANY miles ago and the fatigue has just now took its toll. Loose head bolts can create the same problem, and a leaking injector can shock the head, especially in a diesel.
Then there is always the "it just plain got tired".
New heads are expensive, but far cheaper than another car and will last a LONG time.
Note here, NEW head, if it is temperature or age fatigue, a repaired head will last less than one year. The repair may be great, but the rest of the head is fixing to go.
(Been there done this have the tee shirts.....)