There’s a bit of luck involved and also an element of tolerance and use… You know how sometimes, people say their brakes were fine til they turned the bike upside down, as if it’s just normal? That’s because of air in the system but outside of the pressurised part. So even if you didn’t feel you needed to bleed, maybe there’s still a problem waiting to get you. Or, maybe not- especially if you’re careful, the fluid’s fairly static in the system and unless it moves, there’s nowhere for air to go.
Personally I don’t mind bleeding brakes so I tend to just do it anyway, it only takes minutes. But it’s not always necessary, or even useful. But you kind of need to plan for it.