If Enhanced Estates ever gets implemented, then estates would be actual persistent things that knights would be assigned to. They wouldn't just disappear when the oath dissolves. An estate is a specific size, with specific buildings. When the knight leaves, the estate goes idle, but doesn't disappear. The lord can then assign it to another knight, who inherits the estate and everything on it, fully established. Maybe if it had been idle for too long some of the buildings would eventually fall apart from lack of maintenance. Of course, there's still a lot to be worked out for anything like this to be implemented. But estate revisions was the next big hot topic for the devs to work on.
How is it progressing btw?
I am very exited about it.
From some i hear it's soon and now i hear maybe never