It’s not length of the viva or asking for breaks.
It’s not the opening questions or depth of discussion.
It’s not the number of corrections or when you know the result.
Knowing about all of these things help, but the expectations that really matter are knowing that you are good enough. Knowing that your examiners have prepared. Knowing that you have prepared. Knowing that you’re overwhelmingly likely to succeed.
There are lots of expectations for the viva. There are ranges for many of them and having a sense of what to expect from that variety can give you a sense of what to expect. While you wonder about viva lengths and questions though, pay attention to expectations for you, your examiners, your preparations and your success.
Focus on the expectations that matter.