In 1990 you’d still have quite a few 1980s era machines, and even into 1995 there would be old 8086 machines doing their thing.
But then everything changed when Windows 95 attacked, suddenly the upgrade treadmill was on and those older machines stopped being used not because they were to slow or broken, but because upgraders were dumping used hardware, and you might as well.
Somewhere after the proliferation of SSDs I feel it slowed down again.
I believe it's related to PC standardization really kicking in during the 90's. Before that point, cross-platform abstraction existed but was relatively bespoken to the application, and you couldn't rely on coordination of developers with users that could run out and upgrade to this year's latest, because the pre-32bit desktop hardware kept changing architectures in radically incompatible ways - segmented memory, cooperative multitasking, etc. As such your data export was usually not to another computer, but to paper.
After 1995 you had convergence on Wintel: they won the desktop architecture wars, the address space was large and flat so applications could grow, and Linux, Unicode and the Web were still nascent but all existed in a "right place, right time" sense to drive adoption.
The SSD era slowed things down because right around that time, the focus shifted towards mobile computing, which saw the same treadmill from the start of the iPhone era. The older generation phones of this era are largely uninteresting curios, perhaps valued only if they happen to store an old game that got removed from the stores.
IoT seems to be the next wave, still working towards the big shake-out and standards convergence: "computer as a feature" is increasingly possible to a degree that was unreasonable before.
In 1990 you’d still have quite a few 1980s era machines, and even into 1995 there would be old 8086 machines doing their thing.
But then everything changed when Windows 95 attacked, suddenly the upgrade treadmill was on and those older machines stopped being used not because they were to slow or broken, but because upgraders were dumping used hardware, and you might as well.
Somewhere after the proliferation of SSDs I feel it slowed down again.