http://news.ycombinator.com/classic is a version of the front page sorted only by votes from accounts over one year old. Generally the ranking is not too different, at least for top items. (I know this is not the same thing you're talking about; it just reminded me of it. Also note that /classic was created at a time when there were far fewer accounts that old; perhaps a higher threshold would be more interesting now.)
Personally I've been here for 1472 days (3.5 years) and on the leaderboard for much of that time. I feel like the quality has gone through several up-and-down cycles, though some of that is probably because my tastes have changed too. Overall it feels much as it did several years ago.
Even old-timers rarely browse the /newest page to mod those up. This creates a bias favoring the ranking produced at /news because said old-timers will upvote those more than the ones at /newest (or /classic)
The problem is not only the home page ranking: it's the discussions. I see a lot of low-quality (as in "it's more important to be right than it is to debate in civilized ways") discussions. I did not correlate that to account age.
Source: http://news.ycombinator.com/item?id=607271
Personally I've been here for 1472 days (3.5 years) and on the leaderboard for much of that time. I feel like the quality has gone through several up-and-down cycles, though some of that is probably because my tastes have changed too. Overall it feels much as it did several years ago.