Never was an issue. I think it's because every two weeks we share team stats and it was pretty obvious that we always rushed at the very end of the sprint and needed some process around this.
One hour is the upper limit. In reality, many times people do reviews outside of that window. The official time allocation forces a notification which is the most valuable thing here. That reminder, calls people to action. Sometimes, people will spend the whole hour, if there is some design to discuss for example. Many times it is just a few minutes because you have tiny things to review and you spend the rest of hour doing something else. And other times there is nothing to do.
At the very end, the point is creating the habit.
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