I've had anxiety attacks but I've never let them last more than a minute without taking something. I carry xanax on me and take it before I get too carried away with the whole thing,
On the other hand, I have sometimes felt anxious and nervous for hours, but not a full blown panic, so I just suffered thru until it went away.
Now I have found that exercising helps me burn off extra energy and makes me feel more calm / more relaxed (and a nice side effect is loosing weight and looking better)
Good luck
Good question but it all depends on circumstances and why you are having one. I have had them for they last for about 15 minutes, then have had them where they last for hours! Like yourself, it is benzo time!