Apple's job is to get the device through warranty, at minimum. They look better if they last longer though. Remember how Apple used to be known for a computer that lasted 5 years instead of 2 years? The problem now is that they aren't made that much higher quality than other products (if at all). But if we look at Rossmann he frequently does jobs like retinning connectors. I wouldn't call this disaster recovery since this kind of repair is quite common in electronics in general.

We could probably guesstimate repair failures by looking at industry averages. He could also guesstimate from returning customers. This is how you get an idea of repair failure rates in the first place.

And no, you can't repair at global scale. But why would you need to? There's a reason Toyota doesn't repair every single one of their cars. Or more apt to the conversation: there's a reason Toyota doesn't require you go to a Toyota dealership to get an oil change. It doesn't make sense to. The scale would be ridiculous. There's no reason that electronics needs to be more convoluted than repairing a car. There's no reason a simple fix like a battery swap needs to be more complicated than changing your oil.

> but how reliable are his repairs long term?

So the alternative is to listen to Apple's advice and buy a new device just because they think the device cannot be repaired?