How to ensure long-duration manufacturing of central components?
Although this is not stricty an electronic design question, it is important to most design engineers. Component sourcing is one of our biggest headaches, and most companies are smart in letting a separate person deal with it instead of causing severe depression and anxiety in the engineers.

There are three ways to combat this, aimed at three different tiers of products:


Not-terribly-hard-to-make products should just be adaptable. Say you are making a custom board with expected 100-1000 units production per year. Just design in whatever you want, and when you get a product change notification from the manufacturer that one of the parts is going out of production: use another component and just eat the engineering hours. Terrible as this may sound, this is often economically the best idea in this respect. Even large production runs work well with this model; just produce a new variant of your product that is functionally the same. This is being done in the consumer and professional space all the time.
Small-run, specialist products that took a lot of man hours to make. For instance specialist scientific tools. The best course of action is to do a good estimate of your required components during the service life of the product and buy twice as many components as you will ever need. Cost is rarely a factor, so even though this will cost you quite some money in advance, as well as space to safely store it all, this will be alright. Don't underestimate storing cost: they need to have very specific, tightly controlled atmospheric conditions, especially to ensure solderability.
Medium to large run long term support products. Here, you will want to get a direct line to the manufacturer of your chosen product and ask them to either (a) produce a special version for you with a specified service time or (b) when the PCN goes out, ask them to make those chips specially for you. All MCU companies do this last bit. If you want at least 10.000 chips, even ones that have gone out of production for 20 years, they will happily make them for you - at a nominal fee. However, this is only possible if you need at least in the order of 10 000 units, often even at least 100 000.


Very few companies guarantee any kind of long term support on their components. Even so-called 'design for long term use' automotive parts from Microchip are only guaranteed production parts for 10 years, which is nothing compared to the lifetime of some specialist gear. You will always need to check in directly with manufacturers to ensure availability in the long term.