If it's 0% failure at 200k folds, that means the 200k is about six standard deviations away from the mean, so I think (statistics gurus please correct) that says the average device will last for 1.7m folds.

That can’t be accurate just anecdotally. More likely they call it or or two sds out and chalk up the remaining 10 or so percent as RMAs.

You’re also assuming a normal distribution. This very well might not be a normal distribution

Product lifetime is generally modeled using the Weibull distribution[1]. Depending on the parameters, a normal distribution is a reasonable approximation. Without data on the parameters, and just discussing whether "tested to 200,000 folds" means that every device will survive 200k folds, I think it's fair to use a normal distribution.

Agreed that they probably expect some percentage of RMAs. In fact, I'd argue that "tested to 200k folds" means that 200k gets them enough failures to model the lifetime distribution, so the average lifetime is probably considerably less than 200k.

1. https://www.weibull.com/basics/lifedata.htm

Is it valid to assume a normal distribution here?