Many comedians will admit that getting five minutes of really good material takes years to develop.
If you are dedicated enough, over time, you become funny. Once people see you as funny, it’s difficult to keep being funny.
This is why many comedians go back to stand up. Because no one is just funny all the time. You have to work on it like anything else.
When you are not putting energy into your craft, you are not getting better at it. Obviously. Don’t underestimate the time it takes to put together five good minutes of anything you do. There is a difference between an okay joke and a really good one.