Small continuous upgrades without ever changing your code is the same cost as a gigantic one without ever changing your code - they either work, or they don't, in variously subtle or spectacular ways. The tipping point lies at some changeset, you just need to hit it.

You upgrade, you may need to change things. It's just a fact of life. Or, you pick a library / language / framework / everything that guarantees 100% backwards compatibility as documented, that never has bugs (since fixing those breaks 100% backwards compatibility), and you never use features in even remotely-unexpected ways. Like in this case.