I have a hard time keeping comfrey. It really doesn't like our heat, and it certainly doesn't like being dry. It is the first plant to wilt when the dry sun starts up at this time of year. If I didn't water it regularly, I wouldn't have it.
At the same time, it loathes poor drainage. The easiest way to kill a comfrey for me is to over-water it. So, it's a challenging balancing act. Sometimes I wonder if it's worth the trouble!