All of my adult carpets are 6-7ft. I don’t expect them to get much larger length wise. Life expectancy can be 20+ years. A 4x2x2 or 6x2x2 enclosure would be awesome for an adult carpet. Mine aren’t very active but they do appreciate branches and shelves for climbing and perching. They’re really easy to care for and fun to keep. If he’s healthy then I hope you take the plunge.