What is the life expectancy of someone with lymphoma?

Depends: There are many factors that effect life expectancy including the patients underlying health and the stage of lymphoma. For example lymphoma that is slower growing and has not spread is a better case than a lymphoma that is aggressive and has spread to multiple organs. Hard to answer that question without more information.

Life Expectancy...: Is not a medical term. Cancer studies often report the "median survival" which is the time it takes for 1/2 of patients to die. The other half live longer, and the variation can be large. For highly curable diseases (like some lymphoma types) we often describe the "overall survival" which is the percentage of people alive at a late time point, and is reflective of the cure rate of the disease.