Mits, the silly little greek, just has an aggressive style of posting. He's not trying to offend or pick holes.
He states that the new content will likely be 40+, now by low rate standards these days, that for a player with limited time, could be a month of grinding old euro content. Gone are the days many of us could sit on their computer and smash f buttons for 12hours because we were silly little kids with no work and limited lives
So when we do play, we would like to not be forced into the same caves we've done countless times, and spent countless hours in. Obviously, I've no issue using these caves, it's of course easier to start from a base that we all know, but what Mits wants to get across is that we don't want to be there for too long before new content becomes available / huntable etc.
I also, disagree low rates definitely have more longevity, this is 10000000% down to content etc. a Low rate with sweet fa content will only last longer than a high rate with sweet fa content, because it takes longer for players to get to the end game. I guess, I've contradicted myself a little here, but ultimately, neither last very long at all.
Look at successful high rates such as OS/3h, when Ben ran them. Reasonably well sustained in times of longevity, and it wasn't because it was a low rate and it took ages for players to reach end game. It was because players rarely got to end game before new top tier caves or items were introduced. That to me is how to sustain a server, nothing to do with the rate. I've ended up ranting a little.