I wonder how reliable and durable 7nm chips will be. We might start to see chip failures even after a few years of use.
https://semiengineering.com/transistor-aging-intensifies-10n...
https://semiengineering.com/transistor-aging-intensifies-10n...
Regardless of the absolute number, you can think of it as defining the smallest width of pencil you are used to make a drawing with. You can still use fatter pencils, and in many cases you would want to... shading in a large area for example. But having the smaller pencil lets you put in finer details.
Some thing just won't work if they are too small though, so even though you have a fine sharp pencil available to use, somethings will not change.
Regarding reliability over time, electromigration is the only thing I know of in a typical IC that causes degradation. It is affected by the size of conductors, so potentially things could get worse. It's a well understood phenomenon though so it's usually mitigated by design rules.
Non volatile memories have their own degradation problems.