Quick deployment along with other tactics such as moving are indeed critical in some situations, but .9 seconds is just unrealistic for any but the super competitors.
If you carry and want to get Bill Jordan/Bob Munden quick, you need three things: the right gun, the right holster, and the right technique. Both of the aforementioned gents used different guns, different holsters and different techniques, but had similar results.
At no point were these guys timed while working behind the counter, LOL. But for argument's sake, let's use the Bob Munden standard for what a quick draw should be in a self defense situation. Wait, let's back track. First of all, how many people here are quicker than Bob Munden?
Yeah, I have shot with and competed with some pretty darned fast folks, but none were professional grade like Bob Munden. But they, like Munden had several things in common that your run of the mill robbery victim does not have. They have the luxury of a timed start when THEY ARE READY. When the timer starts, they have already determined how they are going to do what they are going to do on a known course of fire. Their lives were not at risk and they had no concern about bystanders.
If you are Bill Jordan and Bob Munden good, you aren't working at a convenience store, except in the case of Bill Jordan who did it as part of police work specifically to stop robbers. So let's get back to realism. If you are working in a convenience store, chances are you can't afford going to Gunsite 2-3 times a year and putting 500-1000 rounds a week down range. You probably can't afford 100 rounds a week. You aren't sponsored by a department, gun company, ammo company or anyone else.
No, dakota.potts, you cannot be prepared for everything. That is the sad reality. Chances are that if you try to be prepared for everything, you won't have a life outside of trying to be prepared for everything.
You can look for signs and if you watch some of the videos on Youtube, you can often tell when the robber is going to rob the clerk. Of course like with the gun competitions, you already know it is going to happen and so the conclusion that you could tell it was going to happen is really pretty bogus. After you have seen a bunch of people every week that look like they are going to rob you who don't rob you, it becomes hard to tell that you are going to get robbed when it happens. On a given winter day, a clerk may have the store rushed by several customers (just trying to get in from the cold), some wearing masks (it is cold), some who are very agitated, upset, loud, or argumentative (just having a very bad day or are typical jerks), and there will be the furtive actors as well, some of which are just plain paranoid, stoned, etc. If you work in a less than glamorous part of town, you might have a lot of these each day. So 'knowing' you are about to be robbed and being 100% on your game to repel the robbers just isn't a reality for your average Joe Blow clerk. It doesn't matter who you are. Even professionals exposed to repetitive and frequent false alarms are unable to maintain levels of readiness necessary to be properly proficient when the time comes. You can try, but despite the claims of various gun gurus, nobody maintains Condition Yellow all the time.