"Apple's problem is that their products are so good, people aren't upgrading fast enough."
There's nothing about this statement that makes sense. Anyone who understands the current tech landscape knows that it's all about the ecosystem. Regardless of when they upgrade, they will upgrade. Apple's ecosystem lock-in is so much more all encompassing at this point that once you're in there's no reason to leave.
Also, I can't think of a better reason to buy from the same company than 'this lasted way longer than I thought it would'.