Wonderfalls, it's not necessarily about addiction. It's about losing coping skills. If every time your anxiety level hits a certain level, you take your PRN, you'll never learn to manage that level. Of course, if the level is truly unmanagable, it's necessary. But if you also take it when the level is nearly unmanagable, and you do that too often, in the end you'll lose the ability to manage that level and that will also become unmanagable. Your threshhold will lower.

When I was first prescribed PRN benzodiazepines, my pdoc warned me about this. I suggested I write down every time I used it and the reason (basically: day, time, dose, reason (only a few words, maybe 4 or 5 if the reason was particulary complex) and sometimes the location (school, ward, home..), then share it during the appointments. He liked that idea and I did for a long time; almost immediately I also wrote down when I didn't use the PRN even though it might have been warranted, and used/tried to use coping skills alone.
I don't write it down like that anymore, although he does generally ask in session if I've used any that week and how many. I don't always remember exactly, but enough to give an indication.

I use the PRN mostly for these reasons: symptoms are interfering with attending classes at school (or interfering with work); flashbacks (a lot of things count as flashback, but I mean when I actually feel I'm in that situation again. If I don't 'handle' that I'll THINK I'm in that situation again, and I'll be screaming and thrashing about on the ground for about 2 hours. Maybe 90 minutes if I'm lucky. So I take a PRN to help prevent it from getting to that point, also because once I'm in the flashback, I'm not aware enough to take my medication even if someone were to put it to my mouth. I call the first - feeling I'm Back There - an incomplete flashback, and the second - knowing I'm Back There, and behaving as though I am - a complete one); severe anxiety that lasts longer than an hour or two; to settle down to sleep if I'm too agitated and sometimes anxious (unless I'm too afraid to be partially knocked out, then I won't take it). I also often take half a dose before tests; not for the performance anxiety (although it does help with that a little), but to take a tiny bit of the edge of so that if things go wrong, they'll go wrong more slowly and I'll be able to take a full dose before I'm too incapacitated. It depends, if I've had a good few days or week or month trigger/trauma/anxiety-wise, I'll probably not take it.
And sometimes for severe SI urges. I don't usually take them for SUI urges, either I'll 'defeat' the urges by internal motivation or I give in. Well, I might take the PRN if I have the unstoppable urge to use a method I know won't work.
Also for a while I used the sleeping PRN as a knock-out drug: if I was feeling particulary awful and it was 19.00 or after, I'd use the pill and go to sleep. It helped me a lot to be able to escape like that. (My rule for PRN sleeping meds (my pdoc has sometimes changed my PRN to a regular med for a few days or week or even a few weeks, but then I don't count them as PRN even though it's the same drug in the same dose from the same bottle) is that I never take them three nights in a row. (I came up with that 'rule', pdoc thinks it's sort of funny I think) Because I'm ****-retentive like that, that means I never take them two nights in a row: that would mean I wouldn't be able to take them the third night, and what if that third night would be the most awful night ever? (Pdoc thinks that's hilarious. 'You don't want to take it three nights in a row, so you don't take it two nights in a row.')
And I use them if a panic attack is likely and would also be extremely unhelpful. Such as before doctor's visits that I expect (or know) to include an uncomfortable physical observation, or if I'm rather anxious/agitated and have to go to PT or chiropractor (which causes me a lot of anxiety anyway, and I can't get treated if I'm having a panic attack).

Sort of funny is that I've been doing extremely badly these last 5 weeks or so, and if anything, my benzo use only decreased slightly. Mostly because - to paraphrase an email I sent to my pdoc - I use the benzo's to get back into balance, and I'm so far removed from balance it isn't even funny. They don't help enough and I have no idea when to actually use them because I'm totally not OK, never OK at any moment, and can't really define how notOK I am at any given moment.

Funny construction in my country is a PRN Bed-contract. It means you have a 'contract' allowing you to call the crisis ward 24/7 to talk to a nurse, then if that it isn't enough come by and physically have a chat with a nurse, then if that isn't enough stay the night (most are for 24 hours, as is mine, but I also know of 48 or 72-hours. Of course, you can always stay shorter). There are basically two constructions - one is that you can come as often as you want in a set period of time (usually 2 or 3 months, but they can be extended every time. I've had mine for just short of 4 years), the other is that you can come a certain amount of times in as much time as you want (e.g. 3 or 5 or 10 times). Or a combination - x times in 1 month. The 24-hour admission is done by the nurses - the on-call pdoc can be consulted, but that's only if necessary. (Some people have other rules, such as not being allowed to make use of the contract for 24 hours after self injury, drinking, ... because the contract is intended to be used to prevent crisis. Mine doesn't.)
I've called a handful of times, I think two or three times to talk to a nurse and a few more times because I needed something from a pdoc. My mother has also called a few times (e.g. when I was in my one and only manic moment (can't be really called an episode given that it lasted for less than half a day)). And I spent the night once.
(I usually talk to helplines if I want to talk to someone, because I feel at ease calling those just to chat, which I don't feel when calling the ward. I call the ward when I have a clear question or a problem that can be solved; I call a helpline for support. (I once walked away from home to commit suicide, failed, called the ward asking how to get back home. Not sure if I was really not sure how to get back, or if I was asking for help (hey, I did just try to kill myself, just wanted to tell you) and wasn't sure how to phrase it otherwise. Anyway, they had me call my parents or ask permission for them to call them I think? and they picked me up. By the way, a few hours later my own pdoc called me - he was the on-call pdoc that weekend and had heard about my nightly escapade)