Yes, it's much further out on the normal curve. Chip makers have a strong incentive to make chips have long lifetimes. Nobody is going to buy huge volumes of chips that will all die soon. Complicated chips in modern geometries often take many $1M's and often $10M's to develop when you consider the NRE (a few $M's), the tools, and the number of person-years that go into them. If you build chips that die soon, you won't have any customers and that makes it kind of hard to recoup all of those $M's. You really want the product to become obsolete for some other reason than because the chips start dying. If you were creating a mass-market product, would you want to take a $1B write-off on earnings when the world discovered your stuff dies before it's "natural" obsolescence cycle? The general practice is to take the desired lifetime (often 10 years for the server type of chips that I usually build), worst case average temperature, worst case voltage, maximum frequency, pessimistic estimate of how often each signal inside the chip switches, and worst case process variation. A program then applies a formula to each of the structures in the chip design to see if each meets the lifetime expectation with some probability, well over 99%. The models used by these programs take more and more effects into account with each generation. Foundry's work very hard to have good models and work very hard to understand what structures will age poorly and provide design rules to avoid those. Sometimes they mess up and they spend $100M's or more to fix it because their reputation is valuable. For server type applications, the design teams work very hard to be sure that all of the estimates are *not* optimistic. More often, the estimates are fairly pessimistic. The reason is that the probability needs to be really high if you are putting a lot of chips into a box and want the box itself to have a lifetime of 10 years; if a box has 100 chips with only 99% probability of 10 year lifetime, then the contribution 10 years. Bringing this somewhat back on topic ... one of the worst factors in the equation is the average operating temperature. The lifetime falls exponentially with the temperature. If you can get your chips 10 degrees cooler, you will greatly extend their life; make sure boxes have good fans and that the fans are working well. I don't know what fudge factors and design life were used for commercial chips from the '70s, but no matter what the target was, keep it cool! James Markevitch