I believe that we as authors should be able to review the work of our peers and be helpful. I devoted the whole day to this and I hope that the recipient will be thankful. I also hope that the author will reciprocate. The purpose of this is to help us grow a skill set that we can apply to our own work and the assumption is that future work will be easier because we have already worked through these issues.
I am very thankful, and I am in the process of making the reciprocation happen (you’ve managed to pull more free time from your life than I have from mine, or you’re just faster than me).