Well, the scores I give are somewhat relative. As in, an 8/10 means that an episode is well above average next to other episodes of the same show. But if you took an 8/10 on Voyager and compared it to an 8/10 on say TNG or DS9, the latter episodes would win out in my favor.
But you started rating the episodes out of 10 before you knew what the quality of the average episode was really like so does this new rating idea you're now presenting (which I find confusing and really don't like that sfdebris uses it) is only relevant to very recent ratings?
Anyway I don't think the quality of season 6 and season 7 are suddenly much higher rather that you've had a break and are able to now enjoy Voyager for what it is rather than be bogged down by the frustration of expecting better in the former seasons. If you ever rewatch seasons 1/4/5, you'll probably find they're really not that different in quality from 6 and 7.
The same thing happened with me, on a rewatch when my bitterness towards Voyager subsided and learned to enjoy it on it's own merits.
To your first point: It's possible that my older scores are a little less relevant because a certain standard has been defined. In defense of my scoring system, I did not too long ago go back and make slight adjustments to some of my original scores, but only slight adjustments. Nothing has changed by more than one point, and many scores have stayed the same.
And actually, I really do believe the show has reached it's peak in these last two seasons. The show has developed a far stronger sense of continuity, which in turn has allowed for some really great character development. Tom and Belanna have benefited the most, and if they follow up the 7/Chakotay romance that will only help Chakotay's character, who has been sorely underutilized the entire show (although let's be honest, was he ever that interesting to begin with). The writing has also really blossomed, I believe. We've seen a lot of great guest stars these last two seasons and some really meaningful stories that served as more than just filler and really advanced the plot and characters.
EDIT: In season 6 one of my now favorite characters was introduced; Icheb. They've done more with his character than a lot of the regulars who've been with the show since the start. It's like they were bored with what they had, so they decided to throw in someone new and more interesting to spice things up. It worked.