Haha. We wished we got patches. This was back in the day when the prevailing mantra was, "Patches? We don't need no stinking patches!"
(Though we did convince the DBAs to apply a necessary AQ related patch. Rare.)
Having said that, Oracle were pretty good with backwards compatibility regarding their DBs. There was talk of this thing called RAC in the next version. What a dream! That's what I would have gone with to achieve "zero" downtime upgrades. Never got the chance. We used very small patch windows where all boundary processes would stop.