I've been taking Xanax for 2 1/2 years, the .5 dose 3x a day. I find that sometimes I need more than 3x. Therefore, obviously I sometimes run short before I'm due again for a refill. I don't understand the differences between the ones like Xanax that knock the attack out within minutes v. the other benzos that they say have a longer life span in your system. Seems like if I have days where I have to take more Xanax to stop frequent attacks, my doctor would want me to switch to something that would stay in my system longer. Does that make sense? The way I understand it, your body builds of defenses against the Xanax so that it is flushed out more quickly. Well, if you have attacks lets says 3 - 5 times a day (that is what I average), wouldn't you want something that would stay in your system a little longer? I hope this made sense.