If you have bad allergies how often should you be checked?

Depends. As an adult if you have severe food allergies, you might want to be checked every year or so. For pollen allergies, you only need retesting if you have moved to a new region.
Allergies. Depends when you were last checked, how they tested you, and who did the testing. If it has been more than 3 years you really should see an allergist to undergo skin prick testing.