From your GT page (Main page) click on the little gear wheel in the lower left of your screen. Click options, scroll down to network and click on it then click the reset cache button. Purpose is to clear out the buffer that stores up during online activities to make for a smoother experience the next time you are online.
To answer the original post when i've been online for a long period like 4-5 hours my cache stores up so much it takes several minutes to clear it.
When your talking months of not clearing itt out then I'm not surprised it would take 30 minutes or more.