Spent today reviewing some work for an upcoming change to Adept. The PR was close to 5000 lines (includes data files). This effort took most of my morning and also part of my afternoon, but I was also (in parallel) working on getting one of my own PRs code reviewed. Finished the day with my work getting merged. Hoorah for less technical debt.
I feel like code review is a highly underrated, under appreciated part of the work we do. Code review necessarily takes a long time, especially for code that you are also tasked to maintain.