As much as some people complain that Apple is spending too much time resting on its laurels — particularly with the iPhone and certainly the Mac — change has been a constant for the company over the years. In article in AppleInsider about how the Apple II saved Apple, Steve Jobs is quoted as saying that “all computer architectures have about a ten-year life,” but that was largely about boosting the sale of NeXT gear.
Now the ten-year lifecycle comment has in sone respects been true for Apple. So while the Apple II was quite a successful computer in the 1970s, the Mac ultimately supplanted it although it took a while.
Ten years after the Mac debuted in 1984, Apple made a huge change in the processor architecture with the arrival of the PowerPC. Looking back, it wasn’t such an impressive upgrade at first. It took quite a while for apps to be upgraded to the new architecture, so they ran in emulation, and thus much slower than regular Macs of that era.