1999 Dodge Ram Cracked Head

My truck is in the shop now. I took it in because it started running VERY rough. He quickly called me to tell me I had a bad valve. While inspecting the heads he called me in to show me two very small cracks in one head, the other looked OK. My question is this, should I replace both heads while he has the engine torn down? I do not want to spend this much money and have the same problem on the other side and spend the same HUGE chunk of change all over again.

Thanks