noname2200 on 27 April 2009
I originally tried to do micro-repairs on zones which were getting out of hand, but nine out of ten times that just made things worse. All-at-once seems to be the way to go.
Areas go into Prosperity when they gain at least 35 of ALL types of runeys.
I personally left at left eight 3x3 zones unharvested starting in mid-Summer, but that's because my runeys were a mess and I needed each and every last one of them. You could likely get away with much less, if you wish.
And I didn't manage to completely clear out my field until mid-Summer, so don't worry about that. On the other hand, don't do what I did, and plow every square. You need some space for stumps to materialize, or you'll never be able to upgrade your home.
