I had a head gasket let go between two cylinders some time ago. Took it to a local 2nd tier Volvo specialist. When the head came off they informed me of their recommendation to replace the gasket. I asked about taking the opportunity to do some head work. "Why would you want to do that?" was the reply. "It only has 210,000 miles".

Now, at 314,000, I'm beginning to think maybe the bottom end wears out before the head.