I can only speak for myself. I was on one of the largest doses of Xanex for over a year. Was on it for a total of 4 years starting off with a low dose of .5mg twice a day. Then 3 years later finding myself on 2mg three times a day. Personally, I have never had panic attack caused by this drug. Not that some might.
I will say this much, I was told point blank, NEVER stop a Benzodiazapam of any kind (even valium) on you own. Those that have been on it for years have been know to have to go to rehab to recover. Believe me, I have been through withdrawl twice and by the third day I was ready for insanity. I then stayed on them and just recently swtiched to Klonopin (which is also a benzo, so I went from one straight to the other) with just about the same componients so you have no withdrawl at all. I now take 1mg of Klonopin three times a day. Doc says it is a longer acting drug then Xanex is. Stays in you system longer.
I would see you doctore for sure. DON'T stop taking them on your own!