I've never taken a stats course so I really don't know where to begin on this.

I am using microcontroller that according to the datasheet, has a Flash memory that can be reprogrammed a minimum of 10,000 times, with 100,000 times being a more typical number.

These numbers seem low to me (based on other devices using a similar technology which claim lifetimes of an order of magnitude higher), so I decided to take one of our products and do destructive testing on it. I started testing last Friday night and it is already up to 600,000 events without an error (as determined by calculating a 16-bit CRC over the 4K bytes of data test being Flashed). Based on this device far surpassing the "typical" value in the datasheet, I have started tests on three more devices.

So at some point I will have a failure value for all four devices. How can I use that data to predict an expected lifetime x for the device with a 99.9% certainty? (Not sure if I am saying that right, what I mean is that only 0.1% of devices will fail before x events).