It might be useful for us reviewers to discuss what stories need to be reviewed in order of priority, or at least some of the time dip into the pool of older stories that haven't been reviewed in the past. Sometimes you just read a great story and want to tell others about it. And that is fine, but if it is currently on the front page as a new story or even is spending the last couple of weeks on the 30 day new story list, people have seen it and likely will read it before it goes away. Similarly, stories by extremely well known authors likely will not need to be boosted by a new review.
My theory, for what is worth, is that what reviews should do is bring golden or at least gold colored oldies that otherwise likely would remain in obscurity to the attention of a few potential readers, or help those that languish on unvisited author pages, because the author isn't writing new stories. Sometimes a story you like that is older could use a review to encourage the browsing reader who wants something different, and might take a chance on an older story if it has a good review.
Do you other reviewers agree? What makes you decide to spend an hour or maybe less writing a review? If it is already on the top 50 list of stories or has other good reviews, does it make sense to review that story rather than another one with appeal where your review might make a difference?