How pervasive is underestimating project/sprint work to land contracts and expecting devs to make it work in time?

How often are you expected to work more than 8?

It's the norm

Expected?
Outside of major project work, not much, if at all.

I always over estimate, this allows for things to go wrong, things that may be out of your control to go wrong, and more importantly, you get a day each week or two to go "skrew it, I'm doing fuck all today"