Certainly worth the caution, thanks, Miner.

I would like to say that "random failures" wouldn't be the criteria for using the exponential, it would be if the failures were independent of each other, independent of how long the component has been on service, and independent of any external factors, then exponential is a good starting point. The basis of the exponential is - if the probability the item will fail in the next minute (hour, day, year) is the same as the previous minute (hour, day, year) then you generally have an exponential.