> (In practice it's also possible, as Microsoft demonstrated with Windows for decades).
There may be a handful of narrow cases where Microsoft has preserved third-party driver compatibility across long spans of time, but when looking across a decade or more, they break as much as they preserve. Consider DirectX, which is now completely antithetical to its original purpose and name of allowing applications (games) relatively direct hardware access. Modern systems can't survive without a level of hardware abstraction and sharing that mid-90s systems couldn't afford. The end result is that you get essentially no hardware accelerated graphics on decade-old GPUs anymore, except where the drivers were re-written for recent versions of Windows. Vista's new audio subsystem killed off an entire product segment of hardware-accelerated audio processing.
Oh, I meant the demonstration has lasted decades, not necessarily that the backwards-compatibility was eternal. Once you take the stance of preserving compatibility, there's a strong market force to deprecate and eliminate old interfaces and guarantees once it's practical. On both the PC market of then, and the smartphone market of today, hardware gets replaced faster than once per decade.
There may be a handful of narrow cases where Microsoft has preserved third-party driver compatibility across long spans of time, but when looking across a decade or more, they break as much as they preserve. Consider DirectX, which is now completely antithetical to its original purpose and name of allowing applications (games) relatively direct hardware access. Modern systems can't survive without a level of hardware abstraction and sharing that mid-90s systems couldn't afford. The end result is that you get essentially no hardware accelerated graphics on decade-old GPUs anymore, except where the drivers were re-written for recent versions of Windows. Vista's new audio subsystem killed off an entire product segment of hardware-accelerated audio processing.