Not sure why this was necroed, and I won't read all of it, but generally speaking I'm all for shorter worlds.
We are currently 3 months in, and half the villages you can find are either abandoned or kept alive by a single villager who won't give up on the dream of his friends coming back (which they won't, until reset). Few groups survive this long, even fewer last longer.
Right now Mineholes are the main time-gate in this game. One level per week from world start. So you have 2 months / 8 weeks of fresh mining.
By the time level 9 is reached, it's likely that everything else in the game has been experienced (maybe with the exception of whale hunting, which are too hard/boring to find for most players). So what's left? Grinding quality for its own sake.
This is based on an experienced village of 5 to 10 players, not a major faction nor a bot farm. Given how this game is built, I believe it should be calibrated on villages, rather than hermits (which will surely take more time to reach end-game content, but this is clearly a game designed for cooperation rather than single player experience).
So how long should a world last after end-game content has been reached?
I think two months are plenty. That would mean a world should last about 4 or 5 months. Even if we added another month or two, we'd still be far from the year+ a world usually lasts for.
No matter what, shorter worlds should at least be tested. Maybe they'll be good (as I think they will), or maybe they won't. But unless we try there's no way to tell.