Joy Hawkins team did another small local ranking study in Google and found that the longer reviews, the wordier reviews, tend to rank towards the top of the reviews and also stay there for longer.
Joy wrote "Encourage customers to write review longer reviews (100+ words). Since longer reviews tend to stay at the top of a listing for a longer amount of time, this is a good way to ensure that your best reviews stay at the top of a listing for the longest amount of time."
This chart shows that the wordier reviews rank at the top of the reviews on a local listing for a longer period of time:
But this chart shows that the longer, more wordier, reviews tend to be only one-star reviews - which I guess makes sense...
You can check out the study over here. So try to encourage customers who are happy to leave longer reviews. :)
Forum discussion at Twitter.