I read Effortless's review of the BBR 8.9 (nice review), then I read Philpugs, then I punched through to the "All Mountain" ski category and found various model years of the Line Prophet 90 all separately rated (2009, 2010, 2011, 2012). My suggestion would be to drop the year-by-year ratings and to instead aggregate the ratings for each model until something significant (other than topsheet graphics) changes. For example, aggregate the last 3 (4?) years of the pre-rocker Gotama into a single "model," and display the reviews for the rockered Gotama separately. If there was an evolution, with several different versions of "rocker" from the classic Gotama to the current ski, then each substantively different iteration could be listed separately. That way, someone who is interested in a particular ski will be able to see all of the reviews for that model aggregated in one place.
While this proposal sounds like a chore and it might take a bit of research for some people to aggregate the model years correctly, I suspect there are many folks on this site who could do the aggregation I propose without much effort required b/c they know the skis and the models/iterations that have occurred over the years. I don't think it would be necessary to go back more than 5-7 years on any particular ski, unless you want to show off.