I suspect the marginal impact might be pretty high in certain cases. For example, it looks to me as if on iOS you can only be identified down to (browser * iPh

I suspect the marginal impact might be pretty high in certain cases. For example, it looks to me as if on iOS you can only be identified down to (browser * iPhone model * iOS version * timezone). I'd venture a big majority of iPhone users use Safari, most iOS users update their OS fairly quickly, and there aren't that many iPhone models. So battery life could make a big difference there.