It seems like servers that last a year with good reviews tend to survive the longest. If you look at the 12 month range on each rate, you'll see that most servers on the first page have either survived a long time or made a great early impression.
I remember it was changed to six months to help new servers float to the top, but it doesn't seem to have made an impact on the overall quality of private servers. If anything, it brought about more cash grab servers that vanish within a few months after riding a wave of growth driven by clever PR.
Your suggestion is?
Of course you are seeing that because server without review already died and delisted after a year . Those lasted for over 6 months are at least trying and have patience in growing their servers. You don't know how many server went down from 2 weeks to 1 month after opening...