In fact there's plenty of saying no and choosing what to let sit idle happening in my portfolio, so I concur that's just part of being a mature manager. In fact I could point to at least two places in my organization that are somewhat "idle" at the moment where I could actually put additional attention. However creating that bandwidth would break other things.

FWIW, I'm the only one on my team working these kind of hours because we're still establishing our whole organization and my roles are sundry. I also recognize it as an outlier position, so I don't expect anyone to work anything more than the 40 hour week they are being paid for.

I guess rather than talking though specifics though, it's better to ask - when is it reasonable to expect a work schedule like I describe to exist and for how long?

There's no single answer to this, but it's probably a solution to the inputs of product/business maturity, funding and number of personnel with the right skills. If any of those three are "out of balance" people will need to be putting in more work than their pay and job descriptions provide for.

I'm sure being an engineering manager at a FAANG is probably pretty reasonable from a lifestyle perspective.