It is not. But a ton of sites seem to be inconsistent about it, or it feels that way at least. Some sites I frequent don't log me out for months at a time, and

It is not. But a ton of sites seem to be inconsistent about it, or it feels that way at least. Some sites I frequent don't log me out for months at a time, and then suddenly they do. And then they do it again a few weeks later. Followed by multiple months of not doing it once more.