But the turbine generates power to keep the plane flying. Why would it only work for 10 minutes? Certainly the flight time is a product of fuel level and altitude. Even if both engines fail the flight time would be a function of altitude. I don’t see how deployment of the RAT informs flight time.

Well you aren’t constrained by battery if the RAT is deployed, that’s the point of the RAT.

“Probably” is doing a lot of work here, there could be a power failure without engine failure.

/s? A generator or alternator powered directly by the engines is more efficient than towing a wind vane (still indirectly powered by the engines and/or the potential energy of the airplane) every single time.

This discussion has nothing to do with engine out failure modes.

Huh? It’s a generator. It generates minimum power to keep the flight controls and instruments working. It’s not propulsion.