Your ferret is unlike most other mammals, including yourself, because he sleeps a lot. That's not abnormal; it's just what ferrets do. They normally sleep prodigious amounts every day, and even more when they are either sick or older.
The typical ferret sleep pattern is total sleeping time of about 18 out of every 24 hours.
The best things you can do for your ferret's sleep needs is to make it possible for him to sleep easily, deeply, and whenever he wants. Here's what to do: