I've used it for a couple years and agree on it's awesomeness. I use 6 at a time on the edge and 4 on my wife's car, so I order a couple dozen/year. I reapply every 6 months, and it's not even all the way depleted then.
One tip: It's incredibly difficult to wipe it all the way off, but after the application, just wash the car and the surplus will come off without all the tedious buffing.