By the time you are 75 years old how many years will you have spent sleeping?

This will vary by person and can depend on how many hours of sleep you get each night. If you average approximately 7 hours of sleep per night, you can expect to sleep 22 years. If you average 8 hours of sleep per night, you can expect to sleep about 25 years. It is accurate to assume that you will have spent about a third of your life sleeping.