In my experience, tolerance to benzos is a two-part thing. There's the physical tolerance to the chemical, which will lower in time, but there also seems to be a point where you just become "used" to the effects and therefore it takes a higher dose to get the same feeling you used to. I also find on some days benzos will do sweet fuck all, and other days I will get completely munted on far less.
Also, for harm reduction reasons, I suggest that you don't take 12mg of Alprazolam again. For one, unless you have a mighty tolerance, that is a shitload. Xanax -- although shortlasting -- is a very strong benzo, and you can end up getting completely shitfaced and do really stupid things. I ended up in jail for 6 months because I didn't know what I was doing and ended up in someone else's house with a very angry flat full of students who thought I was a burglar. Secondly, a sure-fire way to get a habit and skyrocket your physical dependency/tolerance is to take large doses of benzos, especially when you're already using them daily for medication.
Maybe some of this is incorrect but I'm going from personal experience and my knowledge of benzos isnt as eclectic as it is with opioids so if I'm giving bad advice I'd love to be corrected.
Stay safe,
-OCD