I've just checked the site configuration and registered users should not be being asked to verify they are human using the captcha.

As SilverWarior has stated, your login will timeout if you don't select 'Remember me'.

But, if you are still experiencing the captcha when you are properly logged in, please let me know directly with information (browser, OS etc.) and I'll try and look into it for you with as representative system as I can muster.

Thanks