Page Life Expectancy Wildly Fluctuating
We bumped the memory from 28GB (the original amount) to 40GB, leaving 8GB of memory for the OS and other processes. Immediately afterward everything returned to normal and has stayed stable. One of our DBAs speculated that SQL Server was confused about how much memory it really had available. I had checked the Total Server Memory both before and after and the numbers were consistent with I see in Server Properties but I find that assertion difficult to argue against