Older devices stop getting software/firmware updates.

But usually simpler things like USB to Ethernet adapters and switches don’t have much going on update wise. If anything at all. Switches often do, adapters rarely do.

The best you can do is keep an eye on updates for the devices, if any. Keep an ear out for reported vulnerabilities, and then retire devices when they are no longer maintained.

But all of that is quite a burden for a device most people set up and forget about. At some scale, and in some senses, there is no good answer. New vulnerabilities are found all the time in hardware/software.

If you just mean “will old devices stop working”? No. This would just impact new sales.