As you've alluded to, I think it's circumstantial. Me in my 20s persevered with whatever hunk of junk I was riding until the wheels pretty much fell off. Now in my mid-late 30s, I'd probably feel differently. That said, I don't rely on my bike for anything in particular, and the one I've had for 3 or so years now (Suzuki 250) has been the absolute pinnacle of reliability.
I suspect I'd change it in if it broke down more than twice in a month...