I'm a lot more involved in a cappella now than I was when I started this, and I've heard a lot more, but I try to make sure that a song I score a 5 or a 6 now is not too far off from what it was in the beginning. I do think my scoring has toughened a little bit, but credit for that goes to the overwhelming growth of the art form over the past five years. I've been a RARBer since 1994, I'm thinking, and we got albums from as far back as 1992, so that should give some perspective. They should serve as a point of comparison between the song or album in question and the rest of the a cappella world. And they should also be useful as a point of comparison between the songs on any given album.
Point is an important word.
By their very nature these numbers will not stand up to much in the way of statistical comparison. Albums are reviewed at different times, often with only hazy memory of what came before, and all sorts of factors can come into play. To be truly effective, you'd need something that has unilateral, consistent standards, or at the very least a comprehensive listen to everything being rated. That taken into account, I still think keeping the numbers serves a useful purpose. They are a rough marker for where the song fits in, and when used in conjunction with the comments can be a good guide to where the reviewer thinks the song fits.