What is the projected longevity of classic computer add-ons? I say they are limited to the lifespan of the data in their onboard Flash memory. This is no different than a USB keydrive. As soon as the flash dies, so does the add-on. Modern day add-ons won't last as long as the original hardware.
This all includes anything with Flash, CPLD, FPGA, or even flashcarts/everdrives/harmony/melody. Anything containing non-volatile reprogrammable memory.