The Scrum Guide says that refinement is an “ongoing process”, but what does that mean in practice?
We have complex projects in our product, and we adopted as a practice to sit 2 hours mid-sprint, and groom the backlog. The main reason why we do this, is because many of the topics are very complex, they often require clarifications from the business, so we try to antecipate the questions so we have the answers (so we can estimate the US) once we get to the Sprint Planning meeting.