How common is Gen 2 Head Gasket Failure after 300,000 miles?

I'll simplify the question: The only places where coolant can enter oil are:

1) Head gasket

2) Timing chain cover (RTV seal or damaged cover).

3) Pipe plug in head.

4) Crack/hole in head.

5) Crack/hole in block.

Surely someone here can confirm or dispute.
I'm 99.9% sure, but the reason I am asking is to avoid that "Do'h! All this time it was actually leaking at the ____________!" moment.

 

You sound like a smart guy, but post some odd replies, at leat from time to time, in this case completely missing the question.

The question is: Are the paths/interfaces listed the only places on a gen 2 prius where coolant can theoretically enter the oil?
I think they are. There is no oil cooler in the radiator, for example.

 

Surely many here know?
Are these the only places on a (Gen 2) prius where coolant and oil can mix?

1) Head gasket

2) Timing chain cover (RTV seal or damaged cover).

3) Pipe plug in head (10mm hex key).

4) Crack/hole in head.

5) Crack/hole in block.