If used strictly on a PRN (as needed basis) you could take
Xanax for the rest of your life
and have no problems. But
Xanax is best utilized on a short term basis, <4 months if used daily. For long term anxiety, which after 10 years we can all agree you have, a drug such as Klonopin is as effective as Xanax at controlling not only panic attacks but the anticipatory anxiety that usually comes with severe panic disorder. Best of all, it is prescribed for long term use, as in years.