The typical life span of a mouse is anywhere from 1.5 to 3 years, according to About.com. The average is closer to 1.5 to 2 years, and this limited life span is problematic for people who want to buy mice as pets.
Quality pet stores often separate male and female mice at a young age to preserve their health. Separation protects against early pregnancy in younger mice, which strains the health of females. About.com explains that active mice with bright coloring are the healthiest. Regular cage cleaning along with proper food and water helps to optimize the life span of a pet mouse.