Wild ferrets: They are crepuscular, most active at dawn and dusk, sleeping through most of the day and night. Pet ferrets sleep approximately 14–18 hours per day.
Pet ferrets: They often follow their owners' sleep-wake cycle, active in the evening and sometimes at night. They still require extended sleep periods and may experience "dead sleep" episodes lasting several hours, during which they are completely unresponsive. This is normal and not a cause for concern.
Ferrets sleep so much because it is natural to their biology. Pet ferrets may adjust to their owners' schedules, but they still need significant sleep.