Three factors determine how often you need to enter a two-step authentication code: the authentication settings on the computer you are trying to access, your two-step authentication preferences, and your browser's settings. The authentication settings on the computer you are trying to access are set by the system administrator and are out of your control, but you can adjust your two-step and browser settings.
Next, make sure that all of your web browsers are set to keep cookies and the history. (These settings are usually found in Options or Preferences under Security or Privacy.)
Finally, if it looks like your history and cookie settings are correct but you still have to log in every day, make sure that the webauth_wft cookie is not expiring at the end of every session.