Suggestions to burn his energy:
- Get another cat. This will benefit him in very many ways and will benefit you too because you don't need to worry about playing so often.
- Feeder balls/feeding toys/feeding puzzles
- Electronic cat toys
- Play more
- Cat TV: does he have a window perch? Can he look outside at birds and other things? Even just videos on YouTube labeled "videos for cats to watch" will stimulate his brain
- Clicker training; good for his brain and for the relationship between you and your cat